System and method for sensing distance and/or movement

ABSTRACT

A method (e.g., a method for measuring a separation distance to a target object) includes transmitting an electromagnetic first transmitted signal from a transmitting antenna toward a target object that is a separated from the transmitting antenna by a separation distance. The first transmitted signal includes a first transmit pattern representative of a first sequence of digital bits. The method also includes receiving a first echo of the first transmitted signal that is reflected off the target object, converting the first echo into a first digitized echo signal, and comparing a first receive pattern representative of a second sequence of digital bits to the first digitized echo signal to determine a time of flight of the first transmitted signal and the echo.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/400,261 (now U.S. Pat. No. 9,019,150, which was filed on 20 Feb. 2012(the “'261 Application”), which claims priority benefit to U.S.Provisional Application No. 61/445,026, filed on 21 Feb. 2011 (the “'026Application”) and U.S. Provisional Application No. 61/521,378, filed on9 Aug. 2011 (the “'378 Application”). The entire disclosures of the '261Application, the '026 Application, and the '378 Application areincorporated by reference.

BACKGROUND

One or more embodiments of the subject matter described herein relate todistance and/or motion sensing systems and methods, such as radar and/oroptical remote sensing systems and methods.

Known radar systems transmit analog electromagnetic waves toward targetsand receive echoes of the waves that reflect off the targets. Based onthe distance between antennas that transmit the analog waves and thetarget objects, and/or movement of the target objects, the strengthand/or frequency of the received echoes may change. The strength,frequency, and/or time-of-flight of the echoes may be used to derive thedistance to the targets and/or movement of the targets.

Some known radar systems are limited in the accuracy at which thesystems can measure distances to the targets. For example, theresolution at which these systems may be able to calculate the distanceto targets may be relatively large. Moreover, some of these systems mayhave circuitry, such as a transmit/receive switch, that controls whenthe systems transmit waves or receive echoes. The switch can require anon-zero period of time to allow the systems to switch from transmittingwaves to receiving echoes. This period of time may prevent the systemsfrom being used to measure distances to targets that are relativelyclose, as the transmitted waves may reflect off the targets back to thereceiving antennas before the systems can switch from transmission toreception. Additionally, some known systems have energy leakage from thetransmitting antenna to the receiving antenna. This energy leakage caninterfere with and/or obscure the measurement of distances to thetargets and/or the detection of motion.

BRIEF DESCRIPTION

In one embodiment, a method (e.g., a method for measuring a separationdistance to a target object) is provided. The method includestransmitting an electromagnetic first transmitted signal from atransmitting antenna toward a target object that is a separated from thetransmitting antenna by a separation distance. The first transmittedsignal includes a first transmit pattern representative of a firstsequence of digital bits. The method also includes receiving a firstecho of the first transmitted signal that is reflected off the targetobject, converting the first echo into a first digitized echo signal,and comparing a first receive pattern representative of a secondsequence of digital bits to the first digitized echo signal to determinea time of flight of the first transmitted signal and the echo.

In another embodiment, a system (e.g., a sensing system) is providedthat includes a transmitter, a receiver, and a correlator device. Thetransmitter is configured to generate an electromagnetic firsttransmitted signal that is communicated from a transmitting antennatoward a target object that is a separated from the transmitting antennaby a separation distance. The first transmitted signal includes a firsttransmit pattern representative of a sequence of digital bits. Thereceiver is configured to generate a first digitized echo signal that isbased on an echo of the first transmitted signal that is reflected offthe target object. The correlator device is configured to compare afirst receive pattern representative of a second sequence of digitalbits to the first digitized echo signal to determine a time of flight ofthe first transmitted signal and the echo.

In another embodiment, another method (e.g., for measuring a separationdistance to a target object) is provided. The method includestransmitting a first transmitted signal having waveforms representativeof a first transmit pattern of digital bits and generating a firstdigitized echo signal based on a first received echo of the firsttransmitted signal. The first digitized echo signal includes waveformsrepresentative of a data stream of digital bits. The method alsoincludes comparing a first receive pattern of digital bits to pluraldifferent subsets of the data stream of digital bits in the firstdigitized echo signal to identify a subset of interest that more closelymatches the first receive pattern than one or more other subsets. Themethod further includes identifying a time of flight of the firsttransmitted signal and the first received echo based on a time delaybetween a start of the data stream in the first digitized echo signaland the subset of interest.

BRIEF DESCRIPTION OF THE DRAWINGS

The present subject matter will be better understood from reading thefollowing description of non-limiting embodiments, with reference to theattached drawings, wherein below:

FIG. 1 is a schematic diagram of one embodiment of a sensing system;

FIG. 2 is a schematic diagram of one embodiment of a sensing apparatusshown in FIG. 1;

FIG. 3A is a schematic diagram of a coarse stage determination of a timeof flight for a transmitted signal and corresponding echo in accordancewith one embodiment.

FIG. 3B is another schematic diagram of the coarse stage determinationof a time of flight for a transmitted signal and corresponding echo inaccordance with one embodiment.

FIG. 4 illustrates one example of correlation values that are calculatedand averaged over several transmitted signals shown in FIG. 1;

FIG. 5 is another schematic diagram of part or one implementation of thesensing assembly shown in FIG. 2;

FIG. 6 is a schematic diagram of one embodiment of a front end of thesensing assembly shown in FIG. 2;

FIG. 7 is a circuit diagram of one embodiment of a baseband processingsystem of the system shown in FIG. 1;

FIG. 8 is a schematic diagram of one example of how a comparison devicecompares a bit of interest of a baseband echo signal shown in FIG. 2with a pattern bit of a pattern signal shown in FIG. 2 in oneembodiment;

FIG. 9 illustrates another example of how the comparison device shown inFIG. 7 compares a bit of interest of the baseband echo signal shown inFIG. 2 with a pattern bit of the pattern signal shown in FIG. 2;

FIG. 10 illustrates another example of how the comparison device shownin FIG. 7 compares a bit of interest of the baseband echo signal shownin FIG. 2 with a pattern bit of the pattern signal shown in FIG. 2;

FIG. 11 illustrates examples of output signals shown in FIG. 7 providedby measurement devices shown in FIG. 7 and energy thresholds used by aCPU device shown in FIG. 2 in accordance with one example;

FIG. 12 is a circuit diagram of another embodiment of a basebandprocessing system of the system shown in FIG. 1;

FIG. 13 illustrates projections of in-phase (I) and quadrature (Q)components of a digitized echo signal shown in FIG. 2 in accordance withone embodiment;

FIG. 14 illustrates a technique for distinguishing between echoes shownin FIG. 1 that are reflected off different target objects 104 shown inFIG. 1 in accordance with one embodiment;

FIG. 15 is a schematic view of an antenna in accordance with oneembodiment;

FIG. 16 is a schematic diagram of one embodiment of a front end of thesensing assembly shown in FIG. 1;

FIG. 17 is a cross-sectional view of one embodiment of the antenna shownin FIG. 15 along line 17-17 in FIG. 16;

FIG. 18 illustrates one embodiment of a containment system;

FIG. 19 illustrates one embodiment of a zone restriction system;

FIG. 20 illustrates another embodiment of a volume restriction system;

FIG. 21 is a schematic diagram of one embodiment of a mobile system;

FIG. 22 is a schematic diagram of several object motion vectors inaccordance with one example;

FIG. 23 is a schematic diagram of one example of using the sensingassembly shown in FIG. 1 in a medical application;

FIG. 24 is a two-dimensional image of human subjects in accordance withone example of an application of the system shown in FIG. 1;

FIG. 25 is a schematic diagram of another embodiment of a sensingsystem;

FIG. 26 is a schematic diagram of another embodiment of a sensingsystem;

FIGS. 27A-B illustrate one embodiment of a method for sensing separationdistances from a target object and/or motion of the target object;

FIG. 28 is a schematic diagram of a sensing system in accordance withanother embodiment;

FIG. 29 is a schematic diagram representative of lateral size data of atarget object that is obtained by the sensing system shown in FIG. 28;and

FIG. 30 is another view of a sensing assembly and the target objectshown in FIGS. 28 and 29.

DETAILED DESCRIPTION

In accordance with one or more embodiments of the presently describedinventive subject matter, systems and methods are provided fordetermining distances between a sensing apparatus and one or moretargets. The distances may be determined by measuring times of flight oftransmitted signals (e.g., radar, light, or other signals) that reflectoff the targets. As one example, a signal that includes a known ordesignated transmit pattern (such as waveforms that represent a sequenceof bits) is transmitted and echoes of this signal are received. Thistransmit pattern can be referred to as a coarse stage transmit pattern.The echoes may include information representative of the pattern in thetransmitted signal. For example, the echoes may be received anddigitized to identify a sequence or stream of data that isrepresentative of noise, partial reflections of the transmitted signaloff one or more objects other than the target, and reflections off thetarget.

A coarse stage receive pattern can be compared to the digitized datastream that is based on the received echoes to determine a time offlight of the transmitted signal. The coarse stage receive pattern canbe the same as the transmit pattern or differ from the transmit patternby having a different length and/or sequence of bits (e.g., “0” and“1”). The coarse stage receive pattern is compared to different portionsof the digitized data stream to determine which portion of the datastream more closely matches the receive pattern than one or more otherportions. For example, the coarse stage receive pattern may be shifted(e.g., with respect to time) along the data stream to identify a portionof the data stream that matches the coarse stage receive pattern. A timedelay between the start of the data stream and the matching portion ofthe coarse stage receive pattern may represent the time of flight of thetransmitted signal. This measurement of the time of flight may be usedto calculate a separation distance to the target. As described below,this process for measuring the time of flight may be referred to ascoarse stage determination of the time of flight. The coarse stagedetermination may be performed once or several times in order to measurethe time of flight. For example, a single “burst” of a transmittedsignal may be used to measure the time of flight, or several “bursts” oftransmitted signals (having the same or different transmit patterns) maybe used.

A fine stage determination may be performed in addition to or in placeof the coarse stage determination. The fine stage determination caninclude transmitting one or more additional signals (e.g., “bursts”)toward the target and generating one or more baseband echo signals basedon the received echoes of the signals. The additional signals mayinclude a fine stage transmit pattern that is the same or differentpattern as the coarse stage transmit pattern. The fine stagedetermination can use the time of flight measured by the coarse stagedetermination (or as input by an operator) and compare a fine stagereceive pattern that is delayed by the measured time of flight to acorresponding portion of the data stream. For example, instead ofshifting the fine stage receive pattern along all or a substantialportion of the baseband echo signal, the fine stage receive pattern (ora portion thereof) can be time shifted by an amount that is equal to orbased on the time delay measured by the coarse stage determination.Alternatively, the fine stage receive pattern may be shifted along allor a substantial portion of the baseband echo signal. The time-shiftedfine stage receive pattern can be compared to the baseband echo signalto determine an amount of overlap or, alternatively, an amount ofmismatch between the waveforms of the time-shifted fine stage receivepattern and the baseband echo signal. This amount of overlap or mismatchmay be translated to an additional time delay. The additional time delaycan be added with the time delay measured by the coarse stagedetermination to calculate a fine stage time delay. The fine stage timedelay can then be used to calculate a time of flight and separationdistance to the target.

In one embodiment, an ultrafine stage determination may be performed inaddition to or in place of the coarse stage determination and/or thefine stage determination. The ultrafine stage determination can involvea similar process as the fine stage determination, but using a differentcomponent of the receive pattern and/or the data stream. For example,the fine stage determination may examine the in-phase (I) component orchannel of the receive pattern and the data stream to measure theoverlap or mismatch between the receive pattern and the data stream. Theultrafine stage determination can use the quadrature (Q) component orchannel of the receive pattern and the data stream to measure anadditional amount of overlap or mismatch between the waveforms of thereceive pattern and the data stream. Alternatively, the ultrafine stagedetermination may separately examine the I channel and Q channel of thereceive pattern and the data stream. The use of I and Q channels orcomponents is provided as one example embodiment. Alternatively, one ormore other channels or components may be used. For example, a firstcomponent or channel and a second component or channel may be used,where the first and second components or channels are phase shiftedrelative to each other by an amount other than ninety degrees.

The amounts of overlap or mismatch calculated by the ultrafine stagedetermination can be used to calculate an additional time delay that canbe added to the time delays from the coarse stage and/or the fine stageto determine a time of flight and/or separation distance to the target.Alternatively or additionally, the amount of overlap or mismatch betweenthe waveforms in the I channel and Q channel can be examined to resolvephases of the echoes in order to detect motion of the target.

Alternatively or additionally, the ultrafine stage determination mayinvolve a similar process as the coarse stage determination. Forexample, the coarse stage determination may examine the I channel of thereceive pattern and the data stream to determine correlation values ofdifferent subsets of the data stream and, from those correlation values,determine a subset of interest and a corresponding time-of-flight, asdescribed herein. The ultrafine stage determination can use the Qchannel of the receive pattern and the data stream to determinecorrelation values of different subsets of the data stream and, fromthose correlation values, determine a subset of interest and atime-of-flight. The times-of-flight from the I channel and Q channel canbe combined (e.g., averaged) to calculate a time of flight and/orseparation distance to the target. The correlation values calculated bythe ultrafine stage determination can be used to calculate an additionaltime delay that can be added to the time delays from the coarse stageand/or the fine stage to determine a time of flight and/or separationdistance to the target. Alternatively or additionally, the correlationvalues of the waveforms in the I channel and Q channel can be examinedto resolve phases of the echoes in order to calculate separationdistance or motion of the target.

The coarse, fine, and ultrafine stage determinations can be performedindependently (e.g., without performing one or more of the other stages)and/or together. The fine and ultrafine stage determinations can beperformed in parallel (e.g., with the fine stage determination examiningthe I channel and the ultrafine stage determination examining the Qchannel) or sequentially (e.g., with the ultrafine stage determinationexamining both the I and Q channels). The coarse and ultrafine stagedeterminations can be performed in parallel (e.g., with the coarse stagedetermination examining the I channel and the ultrafine stagedetermination examining the Q channel) or sequentially (e.g., with theultrafine stage determination examining both the I and Q channels).

In one embodiment, a receive pattern mask may be applied to thedigitized data stream to remove (e.g., mask off) or otherwise change oneor more portions or segments of the data stream. The masked data streamcan then be compared to the receive pattern of the corresponding stagedetermination (e.g., coarse stage, fine stage, or ultrafine stage) tomeasure the time of flight, as described herein.

In one embodiment, the various patterns (e.g., the coarse stage transmitpattern, the fine stage transmit pattern, the coarse stage receivepattern, the fine stage receive pattern, and/or the receive patternmask) may be the same. Alternatively, one or more (or all) of thesepatterns may differ from each other. For example, different ones of thepatterns may include different sequences of bits and/or lengths of thesequences. The various patterns (e.g., the coarse stage transmitpattern, the fine stage transmit pattern, the coarse stage receivepattern, the fine stage receive pattern, and/or the receive patternmask) that are used in the ultrafine stage may also differ from thoseused in the coarse or fine stages alone, and from each other.

FIG. 1 is a schematic diagram of one embodiment of a sensing system 100.The system 100 can be used to determine distances between a sensingapparatus 102 and one or more objects 104 and/or to identify movement ofthe one or more target objects 104, where the target objects 104 mayhave positions that may change or that are not known. In one embodiment,the sensing apparatus 102 includes a radar system that transmitselectromagnetic pulse sequences as transmitted signals 106 toward thetarget object 104 that are at least partially reflected as echoes 108.Alternatively, the sensing apparatus 102 can include an optical sensingsystem, such as a LIght Detection And Ranging (LIDAR) system, thattransmits light toward the target object 104 as the transmitted signals106 and receives reflections of the light off the target object 104 asthe echoes 108. In another embodiment, another method of transmissionmay be used, such as sonar, in order to transmit the transmitted signals106 and receive the echoes 108.

A time of flight of the transmitted signals 106 and echoes 108represents the time delay between transmission of the transmittedsignals 106 and receipt of the echoes 108 off of the target object 104.The time of flight can be proportional to a distance between the sensingapparatus 102 and the target object 104. The sensing apparatus 102 canmeasure the time of flight of the transmitted signals 106 and echoes 108and calculate a separation distance 110 between the sensing apparatus102 and the target object 104 based on the time of flight.

The sensing system 100 may include a control unit 112 (“External ControlUnit” in FIG. 1) that directs operations of the sensing apparatus 102.The control unit 112 can include one or more logic-based hardwaredevices, such as one or more processors, controllers, and the like. Thecontrol unit 112 shown in FIG. 1 may represent the hardware (e.g.,processors) and/or logic of the hardware (e.g., one or more sets ofinstructions for directing operations of the hardware that is stored ona tangible and non-transitory computer readable storage medium, such ascomputer software stored on a computer memory). The control unit 112 canbe communicatively coupled (e.g., connected so as to communicate datasignals) with the sensing apparatus 102 by one or more wired and/orwireless connections. The control unit 112 may be remotely located fromthe sensing apparatus 102, such as by being disposed several metersaway, in another room of a building, in another building, in anothercity block, in another city, in another county, state, or country (orother geographic boundary), and the like.

In one embodiment, the control unit 112 can be communicatively coupledwith several sensing assemblies 102 located in the same or differentplaces. For example, several sensing assemblies 102 that are remotelylocated from each other may be communicatively coupled with a commoncontrol unit 112. The control unit 112 can separately send controlmessages to each of the sensing assemblies 102 to individually activate(e.g., turn ON) or deactivate (e.g., turn OFF) the sensing assemblies102. In one embodiment, the control unit 112 may direct the sensingassembly 102 to take periodic measurements of the separation distance110 and then deactivate for an idle time to conserve power.

In one embodiment, the control unit 112 can direct the sensing apparatus102 to activate (e.g., turn ON) and/or deactivate (e.g., turn OFF) totransmit transmitted signals 106 and receive echoes 108 and/or tomeasure the separation distances 110. Alternatively, the control unit112 may calculate the separation distance 110 based on the times offlight of the transmitted signals 106 and echoes 108 as measured by thesensing apparatus 102 and communicated to the control unit 112. Thecontrol unit 112 can be communicatively coupled with an input device114, such as a keyboard, electronic mouse, touchscreen, microphone,stylus, and the like, and/or an output device 116, such as a computermonitor, touchscreen (e.g., the same touchscreen as the input device114), speaker, light, and the like. The input device 114 may receiveinput data from an operator, such as commands to activate or deactivatethe sensing apparatus 102. The output device 116 may present informationto the operator, such as the separation distances 110 and/or times offlight of the transmitted signals 106 and echoes 108. The output device116 may also connect to a communications network, such the internet.

The form factor of the sensing assembly 102 may have a wide variety ofdifferent shapes, depending on the application or use of the system 100.The sensing assembly 102 may be enclosed in a single enclosure 1602,such as an outer housing. The shape of the enclosure 1602 may depend onfactors including, but not limited to, needs for power supply (e.g.,batteries and/or other power connections), environmental protection,and/or other communications devices (e.g., network devices to transmitmeasurements or transmit/receive other communications). In theillustrated embodiment, the basic shape of the sensing assembly 102 is arectangular box. The size of the sensing assembly 102 can be relativelysmall, such as three inches by six inches by two inches (7.6 centimetersby 15.2 centimeters by 5.1 centimeters), 70 mm by 140 mm by 10 mm, oranother size. Alternatively, the sensing assembly 102 may have one ormore other dimensions.

FIG. 2 is a schematic diagram of one embodiment of the sensing apparatus102. The sensing apparatus 102 may be a direct-sequence spread-spectrumradar device that uses a relatively high speed digital pulse sequencethat directly modulates a carrier signal, which is then transmitted asthe transmitted signals 106 toward a target object 104. The echoes 108may be correlated to the same pulse sequence in the transmitted signals106 in order to determine the time of flight of the transmitted signals106 and echoes 108. This time of flight can then be used to calculatethe separation distance 110 (shown in FIG. 1).

The sensing apparatus 102 includes a front end 200 and a back end 202.The front end 200 may include the circuitry and/or other hardware thattransmits the transmitted signals 106 and receives the reflected echoes108. The back end 202 may include the circuitry and/or other hardwarethat forms the pulse sequences for the transmitted signals 106 orgenerates control signals that direct the front end 200 to form thepulse sequences for inclusion in the transmitted signals 106, and/orthat processes (e.g., analyzes) the echoes 108 received by the front end200. Both the front end 200 and the back end 202 may be included in acommon housing. For example (and as described below), the front end 200and the back end 202 may be relatively close to each other (e.g., withina few centimeters or meters) and/or contained in the same housing.Alternatively, the front end 200 may be remotely located from the backend 202. The components of the front end 200 and/or back end 202 areschematically shown as being connected by lines and/or arrows in FIG. 2,which may be representative of conductive connections (e.g., wires,busses, and the like) and/or wireless connections (e.g., wirelessnetworks).

The front end 200 includes a transmitting antenna 204 and a receivingantenna 206. The transmitting antenna 204 transmits the transmittedsignals 106 toward the target object 104 and the receiving antenna 206receives the echoes 108 that are at least partially reflected by thetarget object 104. As one example, the transmitting antenna 204 maytransmit radio frequency (RF) electromagnetic signals as the transmittedsignals 106, such as RF signals having a frequency of 24 gigahertz(“GHz”)±1.5 GHz. Alternatively, the transmitting antenna 204 maytransmit other types of signals, such as light, and/or at anotherfrequency. In the case of light transmission the antenna may be replacedby a laser or LED or other device. The receiver may be replaced by aphoto detector or photodiode.

A front end transmitter 208 (“RF Front-End,” “Transmitter, and/or “TX”in FIG. 2) of the front end 200 is communicatively coupled with thetransmitting antenna 204. The front end transmitter 208 forms andprovides the transmitted signal 106 to the transmitting antenna 204 sothat the transmitting antenna 204 can communicate (e.g., transmit) thetransmitted signal 106. In the illustrated embodiment, the front endtransmitter 208 includes mixers 210A, 210B and an amplifier 212.Alternatively, the front end transmitter 208 may not include theamplifier 212. The mixers 210A, 210B combine (e.g., modulate) a pulsesequence or pattern provided by the back end 202 with an oscillatingsignal 216 (e.g., a carrier signal) to form the transmitted signal 106that is communicated by the transmitting antenna 204. In one embodiment,the mixers 210A, 210B multiply pattern signals 230A, 230B (“Basebandsignal” in FIG. 2) received from one or more transmit (TX) patterngenerators 228A, 228B by the oscillating signal 216. The pattern signal230 includes the pattern formed by the pattern code generator 228. Asdescribed below, the pattern signal 230 can include several bitsarranged in a known or designated sequence.

An oscillating device 214 (“Oscillator” in FIG. 2) of the front end 200generates the oscillating signal 216 that is communicated to the mixers210A, 210B. As one example, the oscillating device 214 may include orrepresent a voltage controlled oscillator (VCO) that generates theoscillating signal 216 based on a voltage signal that is input into theoscillating device 214, such as by a power source (e.g., battery)disposed in the sensing apparatus 102 and/or as provided by the controlunit 112 (shown in FIG. 1). The amplifier 212 may increase the strength(e.g., gain) of the transmitted signal 106.

In the illustrated embodiment, the mixer 210A receives an in-phase (I)component or channel of a pattern signal 230A and mixes the I componentor channel of the pattern signal 230A with the oscillating signal 216 toform an I component or channel of the transmitted signal 106. The mixer210B receives a quadrature (Q) component or channel of a pattern signal230B and mixes the I component or channel of the pattern signal 230Bwith the oscillating signal 216 to form a Q component or channel of thetransmitted signal 106.

The transmitted signal 106 (e.g., one or both of the I and Q channels)is generated when the TX baseband signal 230 flows to the mixers 210.The digital output gate 250 may be disposed between the TX patterngenerator and the mixers 210 for added control of the TX baseband signal230. After a burst of one or more transmitted signals 106 is transmittedby the transmitting antenna 204, the sensing assembly 102 may switchfrom a transmit mode (e.g., that involves transmission of thetransmitted signals 106) to a receive mode to receive the echoes 108 offthe target object 104. In one embodiment, the sensing assembly 102 maynot receive or sense the echoes 108 when in the transmit mode and/or maynot transmit the transmitted signals 106 when in the receive mode. Whenthe sensing assembly 102 switches from the transmit mode to the receivemode, the digital output gate 250 can reduce the amount of time that thetransmit signal 106 generated by the transmitter 208 to the point thatit is eliminated (e.g., reduced to zero strength). For example, the gate250 can include tri-state functionality and a differential highpassfilter (which is represented by the gate 250). The baseband signal 230passes through the filter before the baseband signal 230 reaches theupconversion mixer 210. The gate 250 can be communicatively coupledwith, and controlled by, the control unit 112 (shown in FIG. 1) so thatthe control unit 112 can direct the filter of the gate 250 to enter intoa tri-state (e.g., high-impedance) mode when the transmitted signal 106(or burst of several transmitted signals 106) is transmitted and thesensing assembly 102 is to switch over to receive the echoes 108. Thehighpass filter across differential outputs of the gate 250 can reducethe input transmit signal 106 relatively quickly after the tri-statemode is initiated. As a result, the transmitted signal 106 is preventedfrom flowing to the transmitting antenna 204 and/or from leaking to thereceiving antenna 206 when the sensing assembly 102 receives the echoes108.

A front end receiver 218 (“RF Front-End,” “Receiver,” and/or “RX”) ofthe front end 200 is communicatively coupled with the receiving antenna206. The front end receiver 218 receives an echo signal 224representative of the echoes 108 (or data representative of the echoes108) from the receiving antenna 206. The echo signal 224 may be ananalog signal in one embodiment. The receiving antenna 206 may generatethe echo signal 224 based on the received echoes 108. In the illustratedembodiment, an amplifier 238 may be disposed between the receive antenna206 and the front end receiver 218. The front end receiver 218 caninclude an amplifier 220 and mixers 222A, 222B. Alternatively, one ormore of the amplifiers 220, 238 may not be provided. The amplifiers 220,238 can increase the strength (e.g., gain) of the echo signal 224. Themixers 222A, 222B may include or represent one or more mixing devicesthat receive different components or channels of the echo signal 224 tomix with the oscillating signal 216 (or a copy of the oscillating signal216) from the oscillating device 214. For example, the mixer 222A cancombine the analog echo signal 224 and the I component of theoscillating signal 216 to extract the I component of the echo signal 224into a first baseband echo signal 226A that is communicated to the backend 202 of the sensing apparatus 102. The first baseband echo signal226A may include the I component or channel of the baseband echo signal.The mixer 222B can combine the analog echo signal 224 and the Qcomponent of the oscillating signal 216 to extract the Q component ofthe analog echo signal 224 into a second baseband echo signal 226B thatis communicated to the back end 202 of the sensing apparatus 102. Thesecond baseband echo signal 226B can include the Q component or channelof the baseband echo signal. In one embodiment, the echo signals 226A,226B can be collectively referred to as a baseband echo signal 226. Inone embodiment, the mixers 222A, 222B can multiply the echo signal 224by the I and Q components of the oscillating signal 216 to form thebaseband echo signals 226A, 226B.

The back end 202 of the sensing apparatus 102 includes a transmit (TX)pattern code generator 228 that generates the pattern signal 230 forinclusion in the transmitted signal 106. The transmit pattern codegenerator 228 includes the transmit code generators 228A, 228B. In theillustrated embodiment, the transmit code generator 228A generates the Icomponent or channel pattern signal 230A (“I TX Pattern” in FIG. 2)while the transmit code generator 228B generates the Q component orchannel pattern signal 230B (“Q TX Pattern” in FIG. 2). The transmitpatterns generated by the transmit pattern code generator 228 caninclude a digital pulse sequence having a known or designated sequenceof binary digits, or bits. A bit includes a unit of information that mayhave one of two values, such as a value of one or zero, high or low, ONor OFF, +1 or −1, and the like. Alternatively, a bit may be replaced bya digit, a unit of information that may have one of three or morevalues, and the like. The pulse sequence may be selected by an operatorof the system 100 shown in FIG. 1 (such as by using the input device 114shown in FIG. 1), may be hard-wired or programmed into the logic of thepattern code generator 228, or may otherwise be established.

The transmit pattern code generator 228 creates the pattern of bits andcommunicates the pattern in the pattern signals 230A, 230B to the frontend transmitter 208. The pattern signals 230A, 230B may be individuallyor collectively referred to as a pattern signal 230. In one embodiment,the pattern signal 230 may be communicated to the front end transmitter208 at a frequency that is no greater than 3 GHz. Alternatively, thepattern signal 230 may be communicated to the front end transmitter 208at a greater frequency. The transmit pattern code generator 228 alsocommunicates the pattern signal 230 to a correlator device 232(“Correlator” in FIG. 2). For example, the pattern code generator 228may generate a copy of the pattern signal that is sent to the correlatordevice 232.

The backend section 202 includes or represents hardware (e.g., one ormore processors, controllers, and the like) and/or logic of the hardware(e.g., one or more sets of instructions for directing operations of thehardware that is stored on a tangible and non-transitory computerreadable storage medium, such as computer software stored on a computermemory). The RX backend section 202B receives the pattern signal 230from the pattern code generator 228 and the baseband echo signal 226(e.g., one or more of the signals 226A, 226B) from the front endreceiver 200. The RX backend section 202B may perform one or more stagesof analysis of the baseband echo signal 226 in order to determine theseparation distance 110 and/or to track and/or detect movement of thetarget object 104.

The stages of analysis can include a coarse stage, a fine stage, and/oran ultrafine stage, as described above. In the coarse stage, thebaseband processor 232 compares the pattern signal 230 with the basebandecho signal 226 to determine a coarse or estimated time of flight of thetransmitted signals 106 and the echoes 108. For example, the basebandprocessor 232 can measure a time delay of interest between the time whena transmitted signal 106 is transmitted and a subsequent time when thepattern in the pattern signal 230 (or a portion thereof) and thebaseband echo signal 226 match or substantially match each other, asdescribed below. The time delay of interest may be used as an estimateof the time of flight of the transmitted signal 106 and correspondingecho 108.

In the fine stage, the sensing assembly 102 can compare a replicatedcopy of the pattern signal 230 with the baseband echo signal 226. Thereplicated copy of the pattern signal 230 may be a signal that includesthe pattern signal 230 delayed by the time delay of interest measuredduring the coarse stage. The sensing assembly 102 compares thereplicated copy of the pattern signal 230 with the baseband echo signal226 to determine a temporal amount or degree of overlap or mismatchbetween the replicated pattern signal and the baseband echo signal 226.This temporal overlap or mismatch can represent an additional portion ofthe time of flight that can be added to the time of flight calculatedfrom the coarse stage. In one embodiment, the fine stage examines Iand/or Q components of the baseband echo signal 226 and the replicatedpattern signal.

In the ultrafine stage, the sensing assembly 102 also can examine the Iand/or Q component of the baseband echo signal 226 and the replicatedpattern signal to determine a temporal overlap or mismatch between the Iand/or Q components of the baseband echo signal 226 and the replicatedpattern signal. The temporal overlap or mismatch of the Q components ofthe baseband echo signal 226 and the replicated pattern signal mayrepresent an additional time delay that can be added to the time offlight calculated from the coarse stage and the fine stage (e.g., byexamining the I and/or Q components) to determine a relatively accurateestimation of the time of flight. Alternatively or additionally, theultrafine stage may be used to precisely track and/or detect movement ofthe target object 104 within the bit of interest. The terms “fine” and“ultrafine” are used to mean that the fine stage may provide a moreaccurate and/or precise (e.g., greater resolution) calculation of thetime of flight (t_(F)) and/or the separation distance 110 relative tothe coarse stage and that the ultrafine stage may provide a moreaccurate and/or precise (e.g., greater resolution) calculation of thetime of flight (t_(F)) and/or the separation distance 110 relative tothe fine stage and the coarse stage. Alternatively or additionally, thetime lag of the waveforms in the I channel and Q channel can be examinedto resolve phases of the echoes in order to calculate separationdistance or motion of the target.

As described above, the ultrafine stage determination may involve asimilar process as the coarse stage determination. For example, thecoarse stage determination may examine the I channel of the receivepattern and the data stream to determine correlation values of differentsubsets of the data stream and, from those correlation values, determinea subset of interest and a corresponding time-of-flight, as describedherein. The ultrafine stage determination can use the I and/or Q channelof the receive pattern and the data stream to determine correlationvalues of different subsets of the data stream and, from thosecorrelation values, determine a subset of interest and a time-of-flight.The times-of-flight from the I channel and Q channel can be combined(e.g., averaged) to calculate a time of flight and/or separationdistance to the target. The correlation values calculated by theultrafine stage determination can be used to calculate an additionaltime delay that can be added to the time delays from the coarse stageand/or the fine stage to determine a time of flight and/or separationdistance to the target. Alternatively or additionally, the correlationvalues of the waveforms in the I channel and Q channel can be examinedto resolve phases of the echoes in order to calculate separationdistance or motion of the target.

The backend 202 can include a first baseband processor 232A (“I BasebandProcessor” in FIG. 2) and a second baseband processor 232B (“Q BasebandProcessor” in FIG. 2). The first baseband processor 232A may examine theI component or channel of the echo signal 226A and the second basebandprocessor 232B may examine the Q component or channel of the echo signal226B. The backend 202 can provide a measurement signal 234 as an outputfrom the analysis of the baseband echo signal 226. In one embodiment,the measurement signal 234 includes an I component or channelmeasurement signal 234A from the first baseband processor 232A and a Qcomponent or channel measurement signal 234B from the second basebandprocessor 232B. The measurement signal 234 may include the separationdistance 110 and/or the time of flight. The total position estimate 260can be communicated to the control unit 112 (shown in FIG. 1) so thatthe control unit 112 can use data or information representative of theseparation distance 110 and/or the time of flight for one or more otheruses, calculations, and the like, and/or for presentation to an operatoron the output device 116 (shown in FIG. 1).

As described below, a correlation window that also includes the pattern(e.g., the pulse sequence of bits) or a portion thereof that wastransmitted in the transmitted signal 106 may be compared to thebaseband echo signal 226. The correlation window may be progressivelyshifted or delayed from a location in the baseband echo signal 226representative of a start of the echo signal 226 (e.g., a time thatcorresponds to the time at which the transmitted signal 106 istransmitted, but which may or may not be the exact beginning of thebaseband echo signal) and successively, or in any other order, comparedto different subsets or portions of the baseband echo signal 226.Correlation values representative of degrees of match between the pulsesequence in the correlation window and the subsets or portions of thebaseband echo signal 226 can be calculated and a time delay of interest(e.g., approximately the time of flight) can be determined based on thetime difference between the start of the baseband echo signal 226 andone or more maximum or relatively large correlation values. The maximumor relatively large correlation value may represent at least partialreflection of the transmitted signals 106 off the target object 104, andmay be referred to as a correlation value of interest.

As used herein, the terms “maximum,” “minimum,” and forms thereof, arenot limited to absolute largest and smallest values, respectively. Forexample, while a “maximum” correlation value can include the largestpossible correlation value, the “maximum” correlation value also caninclude a correlation value that is larger than one or more othercorrelation values, but is not necessarily the largest possiblecorrelation value that can be obtained. Similarly, while a “minimum”correlation value can include the smallest possible correlation value,the “minimum” correlation value also can include a correlation valuethat is smaller than one or more other correlation values, but is notnecessarily the smallest possible correlation value that can beobtained.

The time delay of interest can then be used to calculate the separationdistance 110 from the coarse stage. For example, in one embodiment, theseparation distance 110 may be estimated or calculated as:

$\begin{matrix}{d = \frac{t_{F} \times c}{2}} & \left( {{Equation}\mspace{14mu}{\# 1}} \right)\end{matrix}$where d represents the separation distance 110, t_(F) represents thetime delay of interest (calculated from the start of the baseband echosignal 226 to the identification of the correlation value of interest),and c represents the speed of light. Alternatively, c may represent thespeed at which the transmitted signals 106 and/or echoes 108 movethrough the medium or media between the sensing apparatus 102 and thetarget object 104. In another embodiment, the value of t_(F) and/or cmay be modified by a calibration factor or other factor in order toaccount for portions of the delay between transmission of thetransmitted signals 106 and receipt of the echoes 108 that are not dueto the time of flight of the transmitted signals 106 and/or echoes 108.

With continued reference to the sensing assembly 102 shown in FIG. 2,FIGS. 3A and 3B are schematic diagrams of a coarse stage determinationof a time of flight for a transmitted signal 106 and corresponding echo108 in accordance with one embodiment. By “coarse,” it is meant that oneor more additional measurements or analyses of the same or differentecho signal 224 (shown in FIG. 2) that is generated from the reflectedechoes 108 may be performed to provide a more accurate and/or precisemeasurement of the time of flight (t_(F)) and/or separation distance110. The use of the term “coarse” is not intended to mean that themeasurement technique described above is inaccurate or imprecise. Asdescribed above, the pattern generated by the pattern code generator 228and the baseband echo signal 226 are received by the RX backend 202B.The baseband echo signal 226 can be formed by mixing (e.g., multiplying)the echo signal 224 by the oscillating signal 216 in order to translatethe echo signal 224 into a baseband signal.

FIG. 3A illustrates a square waveform transmitted signal 322representative of the transmitted signal 106 (shown in FIG. 1) and thedigitized echo signal 226. The echo signal 226 shown in FIG. 3A mayrepresent the I component or channel of the echo signal 226 (e.g., thesignal 226A). The signals 322, 226 are shown alongside horizontal axes304 representative of time. The transmitted signal 322 includes patternwaveform segments 326 that represent the pattern that is included in thetransmitted signal 106. In the illustrated embodiment, the patternwaveform segments 326 correspond to a bit pattern of 101011, where 0represents a low value 328 of the transmitted signal 322 and 1represents a high value 330 of the transmitted signal 322. Each of thelow or high values 328, 330 occurs over a bit time 332. In theillustrated embodiment, each pattern waveform segment 326 includes sixbits (e.g., six 0s and 1s), such that each pattern waveform segment 326extends over six bit times 332. Alternatively, one or more of thepattern waveform segments 326 may include a different sequence of low orhigh values 328, 330 and/or occur over a different number of bit times332.

The baseband echo signal 226 includes in one embodiment a sequence ofsquare waves (e.g., low and high values 328, 330), but the waves mayhave other shapes. The echo signal 226 may be represented as a digitalecho signal 740 (shown and described below in connection with FIG. 3B).As described below, different portions or subsets of the digital echosignal 740 can be compared to the pattern sequence of the transmittedsignal 106 (e.g., the pattern waveform segments 326) to determine a timedelay of interest, or estimated time of flight. As shown in FIG. 3A, thesquare waves (e.g., low and high values 328, 330) of the baseband echosignal 226 may not exactly line up with the bit times 332 of thetransmitted signal 322.

FIG. 3B illustrates the digitized echo signal 740 of FIG. 3A along theaxis 304 that is representative of time. As shown in FIG. 3B, thedigitized echo signal 740 may be schematically shown as a sequence ofbits 300, 302. Each bit 300, 302 in the digitized echo signal 740 canrepresent a different low or high value 328, 330 (shown in FIG. 3A) ofthe digitized echo signal 740. For example, the bit 300 (e.g., “0”) canrepresent low values 328 of the digitized echo signal 740 and the bit302 (e.g., “1”) can represent high values 330 of the digitized echosignal 740.

The baseband echo signal 226 begins at a transmission time (t₀) of theaxis 304. The transmission time (t₀) may correspond to the time at whichthe transmitted signal 106 is transmitted by the sensing assembly 102.Alternatively, the transmission time (t₀) may be another time thatoccurs prior to or after the time at which the transmitted signal 106 istransmitted.

The baseband processor 232 obtains a receive pattern signal 240 from thepattern generator 228, similar to the transmit pattern (e.g., in thesignal 230) that is included in the transmitted signal 106, the receivepattern signal 240 may include a waveform signal representing a sequenceof bits, such as a digital pulse sequence receive pattern 306 shown inFIG. 3. The baseband processor 232 compares the receive pattern 306 tothe echo signal 226. In one embodiment, the receive pattern 306 is acopy of the transmit pattern of bits that is included in the transmittedsignal 106 from the pattern code generator 228, as described above.Alternatively, the receive pattern 306 may be different from thetransmit pattern that is included in the transmitted signal 106. Forexample, the receive pattern 306 may have a different sequence of bits(e.g., have one or more different waveforms that represent a differentsequence of bits) and/or have a longer or shorter sequence of bits thanthe transmit pattern. The receive pattern 306 may be represented by oneor more of the pattern waveform segments 326, or a portion thereof,shown in FIG. 3A.

The baseband processor 232 uses all or a portion of the receive pattern306 as a correlation window 320 that is compared to different portionsof the digitized echo signal 740 in order to calculate correlationvalues (“CV”) at the different positions. The correlation valuesrepresent different degrees of match between the receive pattern 306 andthe digitized echo signal 740 across different subsets of the bits inthe digitized echo signal 740. In the example illustrated in FIG. 3, thecorrelation window 320 includes six bits 300, 302. Alternatively, thecorrelation window 320 may include a different number of bits 300, 302.The correlator device 731 can temporally shift the correlation window320 along the echo signal 740 in order to identify where (e.g., whichsubset of the echo signal 226) more closely matches the pattern in thecorrelation window 320 more than one or more (or all) of the otherportions of the echo signal 740. In one embodiment, when operating inthe coarse stage determination, the first baseband processor 232Acompares the correlation window 320 to the I component or channel of theecho signal 226.

For example, the correlator device 731 may compare the bits in thecorrelation window 320 to a first subset 308 of the bits 300, 302 in thedigitized echo signal 740. For example, the correlator device 731 cancompare the receive pattern 306 with the first six bits 300, 302 of thedigitized echo signal 740. Alternatively, the correlator device 731 canbegin by comparing the receive pattern 306 with a different subset ofthe digitized echo signal 740. The correlator device 731 calculates afirst correlation value for the first subset 308 of bits in thedigitized echo signal 740 by determining how closely the sequence ofbits 300, 302 in the first subset 308 match the sequence of bits 300,302 in the receive pattern 306.

In one embodiment, the correlator device 731 assigns a first value(e.g., +1) to those bits 300, 302 in the subset of the digitized echosignal 740 being compared to the correlation window 320 that match thesequence of bits 300, 302 in the correlation window 320 and a different,second value (e.g., −1) to those bits 300, 302 in the subset of thedigitized echo signal 740 being examined that do not match the sequenceof bits 300, 302 in the correlation window 320. Alternatively, othervalues may be used. The correlator device 731 may then sum theseassigned values for the subset of the digitized echo signal 740 toderive a correlation value for the subset.

With respect to the first subset 308 of bits in the digitized echosignal, only the fourth bit (e.g., zero) and the fifth bit (e.g., one)match the fourth bit and the fifth bit in the correlation window 320.The remaining four bits in the first subset 308 do not match thecorresponding bits in the correlation window 320. As a result, if +1 isassigned to the matching bits and −1 is assigned to the mismatchingbits, then the correlation value for the first subset 308 of thedigitized echo signal 740 is calculated to be −2. On the other hand, if+1 is assigned to the bits and 0 is assigned to the mismatching bits,then the correlation value for the first subset 308 of the digitizedecho signal 740 is calculated to be +2. As described above, other valuesmay be used instead of +1 and/or −1.

The correlator device 731 then shifts the correlation window 320 bycomparing the sequence of bits 300, 302 in the correlation window 320 toanother (e.g., later or subsequent) subset of the digitized echo signal740. In the illustrated embodiment, the correlator device 731 comparesthe correlation window 320 to the sixth through seventh bits 300, 302 inthe digitized echo signal 740 to calculate another correlation value. Asshown in FIG. 3, the subsets to which the correlation window 320 iscompared may at least partially overlap with each other. For example,each of the subsets to which the correlation window 320 is compared mayoverlap with each other by all but one of the bits in each subset. Inanother example, each of the subsets may overlap with each other by afewer number of the bits in each subset, or even not at all.

The correlator device 731 may continue to compare the correlation window320 to different subsets of the digitized echo signal 740 to calculatecorrelation values for the subsets. In continuing with the aboveexample, the correlator device 731 calculates the correlation valuesshown in FIG. 3 for the different subsets of the digitized echo signal740. In FIG. 3, the correlation window 320 is shown shifted below thesubset to which the correlation window 320 is compared, with thecorrelation value of the subset to which the correlation window 320 iscompared shown to the right of the correlation window 320 (using valuesof +1 for matches and −1 for mismatches). As shown in the illustratedexample, the correlation value associated with the fifth through tenthbits 300, 302 in the digitized echo signal 226 has a correlation value(e.g., +6) that is larger than one or more other correlation values ofthe other subsets, or that is the largest of the correlation values.

In another embodiment, the receive pattern 306 that is included in thecorrelation window 320 and that is compared to the subsets of thedigitized echo signal 740 may include a portion, and less than theentirety, of the transmit pattern that is included in the transmittedsignal 106 (shown in FIG. 1). For example, if the transmit pattern inthe transmitted signal 106 includes a waveform representative of adigital pulse sequence of thirteen (or a different number) of bits 300,302, the correlator device 731 may use a receive pattern 306 thatincludes less than thirteen (or a different number) of the bits 300, 302included in the transmit pattern.

In one embodiment, the correlator device 731 can compare less than theentire receive pattern 306 to the subsets by applying a mask to thereceive pattern 306 to form the correlation window 320 (also referred toas a masked receive pattern). With respect to the receive pattern 306shown in FIG. 3, the correlator device 731 may apply a mask comprisingthe sequence “000111” (or another mask) to the receive pattern 306 toeliminate the first three bits 300, 302 from the receive pattern 306such that only the last three bits 300, 302 are compared to the varioussubsets of the digitized echo signal 740. The mask may be applied bymultiplying each bit in the mask by the corresponding bit in the receivepattern 306. In one embodiment, the same mask also is applied to each ofthe subsets in the digitized echo signal 740 when the correlation window320 is compared to the subsets.

The correlator 731 may identify a correlation value that is largest,that is larger than one or more correlation values, and/or that islarger than a designated threshold as a correlation value of interest312. In the illustrated example, the fifth correlation value (e.g., +6)may be the correlation value of interest 312. The subset or subsets ofbits in the digitized echo signal 740 that correspond to the correlationvalue of interest 312 may be identified as the subset or subsets ofinterest 314. In the illustrated example, the subset of interest 314includes the fifth through tenth bits 300, 302 in the digitized echosignal 740. In this example, if the start of the subset of interest isused to identify the subset of interest then the delay of interest wouldbe five. Multiple subsets of interest may be identified where thetransmitted signals 106 (shown in FIG. 1) are reflected off of multipletarget objects 104 (shown in FIG. 1), such as different target objects104 located different separation distances 110 from the sensing assembly102.

Each of the subsets of the digitized echo signal 740 may be associatedwith a time delay (t_(d)) between the start of the digitized echo signal740 (e.g., t₀) and the beginning of the first bit in each subset of thedigitized echo signal 740. Alternatively, the beginning of the timedelay (t_(d)) for the subset can be measured from another starting time(e.g., a time before or after the start of the digitized echo signal 740(t₀) and/or the end of the time delay (t_(d)) may be at another locationin the subset, such as the middle or at another bit of the subset.

The time delay (t_(d)) associated with the subset of interest mayrepresent the time of flight (t_(F)) of the transmitted signal 106 thatis reflected off a target object 104. Using Equation #1 above, the timeof flight can be used to calculate the separation distance 110 betweenthe sensing assembly 102 and the target object 104. In one embodiment,the time of flight (t_(F)) may be based on a modified time delay(t_(d)), such as a time delay that is modified by a calibration factorto obtain the time of flight (t_(F)). As one example, the time of flight(t_(F)) can be corrected to account for propagation of signals and/orother processing or analysis. Propagation of the echo signal 224,formation of the baseband echo signal 226, propagation of the basebandecho signal 226, and the like, through the components of the sensingassembly 102 can impact the calculation of the time of flight (t_(F)).The time delay associated with a subset of interest in the baseband echosignal 226 may include the time of flight of the transmitted signals 106and echoes 108, and also may include the time of propagation of varioussignals in the analog and digital blocks (e.g., the correlator device731 and/or the pattern code generator 228 and/or the mixers 210 and/orthe amplifier 238) of the system 100.

In order to determine the propagation time of data and signals throughthese components, a calibration routine can be employed. A measurementcan be made to a target of known distance. For example, one or moretransmitted signals 106 can be sent to the target object 104 that is ata known separation distance 110 from the transmit and/or receivingantennas 204, 206. The calculation of the time of flight for thetransmitted signals 106 can be made as described above, and the time offlight can be used to determine a calculated separation distance 110.Based on the difference between the actual, known separation distance110 and the calculated separation distance 110, a measurement error thatis based on the propagation time through the components of the sensingassembly 102 may be calculated. This propagation time may then be usedto correct (e.g., shorten) further times of flight that are calculatedusing the sensing assembly 102.

In one embodiment, the sensing assembly 102 may transmit several burstsof the transmitted signal 106 and the correlator device 731 maycalculate several correlation values for the digitized echo signals 740that are based on the reflected echoes 108 of the transmitted signals106. The correlation values for the several transmitted signals 106 maybe grouped by common time delays (t_(d)), such as by calculating theaverage, median, or other statistical measure of the correlation valuescalculated for the same or approximately the same time delays (t_(d)).The grouped correlation values that are larger than other correlationvalues or that are the largest may be used to more accurately calculatethe time of flight (t_(F)) and separation distance 110 relative to usingonly a single correlation value and/or burst.

FIG. 4 illustrates one example of correlation values that are calculatedand averaged over several transmitted signals 106 shown in FIG. 1. Thecorrelation values 400 are shown alongside a horizontal axis 402representative of time (e.g., time delays or times of flight) and avertical axis 404 representative of the magnitude of the correlationvalues 400. As shown in FIG. 4, several peaks 406, 408 may be identifiedbased on the multiple correlation values 400 that are grouped overseveral transmitted signals 106. The peaks 406, 408 may be associatedwith one or more target objects 104 (shown in FIG. 1) off which thetransmitted signals 106 reflected. The time delays associated with oneor more of the peaks 406, 408 (e.g., the time along the horizontal axis402) can be used to calculate the separation distance(s) 110 of one ormore of the target objects 104 associated with the peaks 406, 408, asdescribed above.

FIG. 5 is another schematic diagram of the sensing assembly 102 shown inFIG. 2. The sensing assembly 102 is illustrated in FIG. 5 as including aradio front end 500 and a processing back end 502. The radio front end500 may include at least some of the components included in the frontend 200 (shown in FIG. 2) of the sensing assembly 102 and the processingback end 502 may include at least some of the components of the back end202 (shown in FIG. 2) of the sensing assembly 102, and/or one or morecomponents (e.g., the front end transmitter 208 and/or receiver 218shown in FIG. 2) of the front end 200.

As described above, the received echo signal 224 may be conditioned bycircuits 506 (e.g., by the front end receiver 218 shown in FIG. 2) thatare used for high-speed optical communications systems in oneembodiment. This conditioning may include amplification and/orquantization only. The signal 224 may then pass to a digitizer 730 thatcreates a digital signal based on the signal 224, which is then passedto the correlator 731 (described below) for comparison to the originaltransmit sequence to extract time-of-flight information. The correlatordevice 731 and the conditioning circuits may be collectively referred toas the baseband processing section of the sensing apparatus 102.

Also as described above, the pattern code generator 228 generates thepattern (e.g., a digital pulse sequence) that is communicated in thepattern signal 230. The digital pulse sequence may be relatively highspeed in order to make the pulses shorter and increase accuracy and/orprecision of the system 100 (shown in FIG. 1) and/or to spread thetransmitted radio energy over a very wide band. If the pulses aresufficiently short enough, the bandwidth may be wide enough to beclassified as Ultra-wideband (UWB). As a result, the system 100 can beoperated in the 22-27 GHz UWB band and/or the 3-10 GHz UWB band that areavailable worldwide (with regional variations) for unlicensed operation.

In one embodiment, the digital pulse sequence is generated by one ormore digital circuits, such as a relatively low-power Field-ProgrammableGate Array (FPGA) 504. The FPGA 504 may be an integrated circuitdesigned to be configured by the customer or designer aftermanufacturing to implement a digital or logical system. As shown in FIG.5, the FPGA 504 can be configured to perform the functions of the pulsecode generator 228 and the correlator device 731. The pulse sequence canbe buffered and/or conditioned by one or more circuits 508 and thenpassed directly to the transmit radio of the front end 500 (e.g., thefront end transmitter 208).

FIG. 6 is a schematic diagram of one embodiment of the front end 200 ofthe sensing assembly 102 shown in FIG. 2. The front end 200 of thesensing assembly 102 may alternatively be referred to as the radio frontend 500 (shown in FIG. 5) or the “radio” of the sensing assembly 102. Inone embodiment, the front end 200 includes a direct-conversiontransmitter 600 (“TX Chip” in FIG. 6) and receiver 602 (“RX Chip” inFIG. 6), with a common frequency reference generator 604 (“VCO Chip” inFIG. 6). The transmitter 600 may include or represent the front endtransmitter 208 (shown in FIG. 2) and the receiver 602 may include orrepresent the front end receiver 218 (shown in FIG. 2).

The common frequency reference generator 604 may be or include theoscillator device 214 shown in FIG. 2. The common frequency referencegenerator 604 may be a voltage-controlled oscillator (VCO) that producesa frequency reference signal as the oscillating signal 216. In oneembodiment, the frequency of the reference signal 216 is one half of adesignated or desired carrier frequency of the transmitted signal 106(shown in FIG. 1). Alternatively, the reference signal 216 may beanother frequency, such as the same frequency as the carrier frequency,an integer multiple or divisor of the carrier frequency, and the like.

In one embodiment, the reference generator 604 emits a frequencyreference signal 216 that is a sinusoidal wave at one half the frequencyof the carrier frequency. The reference signal is split equally anddelivered to the transmitter 600 and the receiver 602. Although thereference generator 604 may be able to vary the frequency of thereference signal 216 according to an input control voltage, thereference generator 604 can be operated at a fixed control voltage inorder to cause the reference generator 604 to output a fixed frequencyreference signal 216. This is acceptable since frequency coherencebetween the transmitter 600 and the receiver 602 may be automaticallymaintained. Furthermore, this arrangement can allow for coherencebetween the transmitter 600 and the receiver 602 without the need for aphase locked loop (PLL) or other control structure that may limit theaccuracy and/or speed at which the sensing assembly 102 operates. Inanother embodiment a PLL may be added to for other purposes, such asstabilizing the carrier frequency or otherwise controlling the carrierfrequency.

The reference signal 216 can be split and sent to the transmitter 600and receiver 602. The reference signal 216 drives the transmitter 600and receiver 602, as described above. The transmitter 600 may drive(e.g., activate to transmit the transmitted signal 106 shown in FIG. 1)the transmitting antenna 204 (shown in FIG. 2). The receiver 602 mayreceive the return echo signal through the receiving antenna 206 (shownin FIG. 2) that is separate from the transmitting antenna 204. This canreduce the need for a T/R (transmit/receive) switch disposed between thetransmitter 600 and the receiver 602. The transmitter 600 can up-convertthe timing reference signal 216 and transmit an RF transmit signal 606through the transmitting antenna 204 in order to drive the transmittingantenna 204 to transmit the transmitted signal 106 (shown in FIG. 1). Inone embodiment, the output of the transmitter 600 can be at a maximumfrequency or a frequency that is greater than one or more otherfrequencies in the sensing assembly 102 (shown in FIG. 1). For example,the transmit signal 606 from the transmitter 600 can be at the carrierfrequency. This transmit signal 606 can be fed directly to thetransmitting antenna 204 to minimize or reduce the losses incurred bythe transmit signal 606.

In one embodiment, the transmitter 600 can take separate in-phase (I)and quadrature (Q) digital patterns or signals from the patterngenerator 604 and/or the pattern code generator 228 (shown in FIG. 2).This can allow for increased flexibility in the transmit signal 606and/or can allow for the transmit signal 606 to be changed “on the fly,”or during transmission of the transmitted signals 106.

As described above, the receiver 602 may also receive a copy of thefrequency reference signal 216 from the reference generator 604. Thereturning echoes 108 (shown in FIG. 1) are received by the receivingantenna 206 (shown in FIG. 2) and may be fed directly to the receiver602 as the echo signal 224. This arrangement can give the system maximumor increased possible input signal-to-noise ratio (SNR), since the echosignal 224 propagates a minimal or relatively small distance before theecho signal 224 enters the receiver 602. For example, the echo signal224 may not propagate or otherwise go through a switch, such as atransmit/receive (TX/RX) switch.

The receiver 602 can down-convert a relatively wide block of frequencyspectrum centered on the carrier frequency to produce the basebandsignal (e.g., the baseband echo signal 226 shown in FIG. 2). Thebaseband signal may then be processed by a baseband analog section ofthe sensing assembly 102 (shown in FIG. 1), such as the correlatordevice 731 (shown in FIG. 2) and/or one or more other components, toextract the time of flight (t_(F)). As described above, this receivedecho signal 224 includes a delayed copy of the TX pattern signal. Thedelay may be representative of and/or is a measurement of theround-trip, time-of-flight of the transmitted signal 106 and thecorresponding echo 108.

The frequency reference signal 216 may contain or comprise two or moreindividual signals such as the I and Q components that are phase shiftedrelative to each other. The phase shifted signals can also be generatedinternally by the transmitter 600 and the receiver 602. For example, thesignal 216 may be generated to include two or more phase shiftedcomponents (e.g., I and Q components or channels), or may be generatedand later modified to include the two or more phase shifted components.

In one embodiment, the front end 200 provides relatively high isolationbetween the transmit signal 606 and the echo signal 224. This isolationcan be achieved in one or more ways. First, the transmit and receivecomponents (e.g., the transmitter 600 and receiver 602) can be disposedin physically separate chips, circuitry, or other hardware. Second, thereference generator 604 can operate at one half the carrier frequency sothat feed-through can be reduced. Third, the transmitter 600 and thereceiver 602 can have dedicated (e.g., separate) antennas 204, 206 thatare also physically isolated from each other. This isolation can allowfor the elimination of a TX/RX switch that may otherwise be included inthe system 100. Avoiding the use of the TX/RX switch also can remove theswitch-over time between the transmitting of the transmitted signals 106and the receipt of the echoes 108 shown in FIG. 1. Reducing theswitch-over time can enable the system 100 to more accurately and/orprecisely measure distances to relatively close target objects 104. Forexample, reducing this switch-over time can reduce the thresholddistance that may be needed between the sensing assembly 102 and thetarget object 104 in order for the sensing assembly 102 to measure theseparation distance 110 shown in FIG. 1 before transmitted signals 106are received as echoes 108.

FIG. 7 is a circuit diagram of one embodiment of a baseband processingsystem 232 of the system 100 shown in FIG. 1. In one embodiment, thebaseband processing system 232 is included in the sensing assembly 102(shown in FIG. 1) or is separate from the system 100 but operativelycoupled with the system 100 to communicate one or more signals betweenthe systems 100, 232. For example, the baseband processing system 232can be coupled with the front end receiver 218 (shown in FIG. 2) toreceive the echo signal 226 (e.g., the echo signal 226A and/or 226B).For example, at least part of the system 232 may be disposed between thefront end receiver 218 and the Control and Processing Unit (CPU) 270shown in FIG. 7. The baseband processing system 232 may provide for thecoarse and/or fine and/or ultrafine stage determinations describedabove.

In one embodiment, the system 100 (shown in FIG. 1) includes a finetransmit pattern (e.g., a transmit pattern for fine stage determination)in the transmitted signal 106 following the coarse stage determination.For example, after transmitting a first transmit pattern in a firsttransmitted signal 106 (or one or more bursts of several transmittedsignals 106) to use the coarse stage and calculate a time delay in theecho signal 226 (and/or the time of flight), a second transmit patterncan be included in a subsequent, second transmitted signal 106 for thefine stage determination of the time of flight (or a portion thereof).The transmit pattern in the coarse stage may be the same as the transmitpattern in the fine stage. Alternatively, the transmit pattern of thefine stage may differ from the transmit pattern of the coarse stage,such as by including one or more different waveforms or bits in a pulsesequence pattern of the transmitted signal 106.

The baseband processing system 232 receives the echo signal 226 (e.g.,the I component or channel of the echo signal 226A and/or the Qcomponent or channel of the echo signal 226B from the front end receiver218 (shown in FIG. 1). The echo signal 226 that is received from thefront end receiver 218 is referred to as “I or Q Baseband signal” inFIG. 7. As described below, the system 232 also may receive a receivepattern signal 728 (“I or Q fine alignment pattern” in FIG. 7) from thepattern code generator 228 (shown in FIG. 2). Although not shown in FIG.2 or 7, the pattern code generator 228 and the system 232 may be coupledby one or more conductive pathways (e.g., busses, wires, cables, and thelike) to communicate with each other. The system 232 can provide outputsignals 702A, 702B (collectively or individually referred to as anoutput signal 702 and shown as “Digital energy estimates for I or Qchannel” in FIG. 7). In one embodiment, the baseband processing system232 is an analog processing system. In another embodiment, the basebandprocessing system 232 is a hybrid analog and digital system comprised ofcomponents and signals that are analog and/or digital in nature.

The digitized echo signal 226 that is received by the system 232 may beconditioned by signal conditioning components of the baseband processingsystem 232, such as by modifying the signals using a conversionamplifier 704 (e.g., an amplifier that converts the baseband echo signal226, such as by converting current into a voltage signal). In oneembodiment, the conversion amplifier 704 includes or represents atrans-impedance amplifier, or “TIA” in FIG. 7). The signal conditioningcomponents can include a second amplifier 706 (e.g., a limitingamplifier or “Lim. Amp” in FIG. 7). The conversion amplifier 704 canoperate on a relatively small input signal that may be a single-ended(e.g., non-differential) signal to produce a differential signal 708(that also may be amplified and/or buffered by the conversion amplifier704 and/or one or more other components). This differential signal 708may still be relatively small in amplitude. In one embodiment, thedifferential signal 708 is then passed to the second amplifier 706 thatincreases the gain of the differential signal 708. Alternatively, thesecond amplifier 706 may not be included in the system 232 if theconversion amplifier 704 produces a sufficiently large (e.g., in termsof amplitude and/or energy) output differential signal 710. The secondamplifier 706 can provide relatively large gain and can toleratesaturated outputs 710. There may be internal positive feedback in thesecond amplifier 706 so that even relatively small input differences inthe differential signal 708 can produce a larger output signal 710. Inone embodiment, the second amplifier 706 quantizes the amplitude of thereceived differential signal 708 to produce an output signal 710.

The second amplifier 706 may be used to determine the sign of the inputdifferential signal 708 and the times at which the sign changes from onevalue to another. For example, the second amplifier 706 may act as ananalog-to-digital converter with only one bit precision in oneembodiment. Alternatively, the second amplifier 706 may be a high-speedanalog-to-digital converter that periodically samples the differentialsignal 708 at a relatively fast rate. Alternatively, the secondamplifier may act as an amplitude quantizer while preserving timinginformation of the baseband signal 226. The use of a limiting amplifieras the second amplifier 706 can provide relatively high gain andrelatively large input dynamic range. As a result, relatively smalldifferential signals 708 that are supplied to the limiting amplifier canresult in a healthy (e.g., relatively high amplitude and/orsignal-to-noise ratio) output signal 710. Additionally, largerdifferential signals 708 (e.g., having relatively high amplitudes and/orenergies) that may otherwise result in another amplifier beingoverdriven instead result in a controlled output condition (e.g., thelimiting operation of the limiting amplifier). The second amplifier 706may have a relatively fast or no recovery time, such that the secondamplifier 706 may not go into an error or saturated state and maycontinue to respond to the differential signals 708 that are input intothe second amplifier 706. When the input differential signal 708 returnsto an acceptable level (e.g., lower amplitude and/or energy), the secondamplifier 706 may avoid the time required by other amplifiers forrecovery from an overdrive state (that is caused by the inputdifferential signal 708). The second amplifier 706 may avoid losingincoming input signals during such a recovery time.

A switch device 712 (“Switch” in FIG. 7) that receives the outputdifferential signal 710 (e.g., from the second amplifier 706) cancontrol where the output differential signal 710 is sent. For example,the switch device 712 may alternate between states where, in one state(e.g., a coarse acquisition or determination state), the switch device712 directs the output differential signal 710 along a first path 716 tothe digitizer 730 and then to the correlator device 731. The digitizer730 includes one or more analog or digital components, such as aprocessor, controller, buffers, digital gates, delay lines, samplers andthe like, that digitize received signals into a digital signal, such asthe digital echo signal 740 described above in connection with FIG. 3B.The first path 716 is used to provide for the coarse stage determinationof the time of flight, as described above. In one embodiment, thesignals 710 may pass through another amplifier 714 and/or one or moreother components before reaching the correlator device 731 for thecoarse stage determination. In another state, the switch device 712directs the output differential signal 710 along a different, secondpath 718 to one or more other components (described below). The secondpath 718 is used for the fine stage determination of the time of flightin the illustrated embodiment.

The switch device 712 may alternate the direction of flow of the signals(e.g., the output differential signal 710) from the first path 716 tothe second path 718. Control of the switch device 712 may be provided bythe control unit 112 (shown in FIG. 1). For example, the control unit112 may communicate control signals to the switch device 712 to controlwhere the signals flow after passing through the switch device 712.

The output differential signals 710 received by the switch device 712may be communicated to a comparison device 720 in the second path 718.Alternatively, the switch device 712 (or another component) may convertthe differential signals 710 into a single-ended signal that is inputinto the comparison device 720. The comparison device 720 also receivesthe receive pattern signal 728 from the pattern generator 228 (shown inFIG. 2). The receive pattern signal 728 is referred to as “I or Q finealignment pattern” in FIG. 7). The receive pattern signal 728 mayinclude a copy of the same transmit pattern that is transmitted in thetransmitted signal 106 used to generate the echo signal 226 beinganalyzed by the system 232. Alternatively, the receive pattern signal728 may differ from the transmit signal that is transmitted in thetransmitted signal 106 used to generate the echo signal 226 beinganalyzed by the system 232.

The comparison device 720 compares the signals received from the switchdevice 712 with the receive pattern signal 728 to identify differencesbetween the echo signal 226 and the receive pattern signal 728.

In one embodiment, the receive pattern signal 728 includes a patternthat is delayed by the time delay (e.g., the time of flight) identifiedby the coarse stage determination. The comparison device 720 may thencompare this time-delayed pattern in the pattern signal 728 to the echosignal 226 (e.g., as modified by the amplifiers 704, 710) to identifyoverlaps or mismatches between the time-delayed pattern signal 728 andthe echo signal 226.

In one embodiment, the comparison device 720 may include or represent alimiting amplifier that acts as a relatively high-speed XOR gate. An“XOR gate” includes a device that receives two signals and produces afirst output signal (e.g., a “high” signal) when the two signals aredifferent and a second output signal (e.g., a “low” signal) or no signalwhen the two signals are not different.

In another embodiment, the system may only include the coarse basebandprocessing circuits 716 or the fine baseband processing circuits 718. Inthis case, the switch 712 may also be eliminated. For example, this maybe to reduce the cost or complexity of the overall system. As anotherexample, the system may not need the fine accuracy and the rapidresponse of the coarse section 716 is desired. The coarse, fine andultrafine stages may be used in any combination at different times inorder to balance various performance metrics. Intelligent control can bemanually provided by an operator or automatically generated by aprocessor or controller (such as the control unit 112) autonomouslycontrolling the assembly 102 based on one or more sets of instructions(such as software modules or programs) stored on a tangible computerreadable storage medium (such as a computer memory). The intelligentcontrol can manually or automatically switch between which stages areused and/or when based on feedback from one or more other stages. Forexample, based on the determination from the coarse stage (e.g., anestimated time of flight or separation distance), the sensing assembly102 may manually or automatically switch to the fine and/or ultrafinestage to further refine the time of flight or separation distance and/orto monitor movement of the target object 104.

With continued reference to FIG. 7, FIG. 8 is a schematic diagram of oneexample of how the comparison device 720 compares a portion 800 of thebaseband echo signal 226 with a portion 802 of the time-delayed patternsignal 728 in one embodiment. Although only portions 800, 802 of thepattern signal 728 and the echo signal 226 are shown, the comparisondevice 720 may compare more, or all, of the echo signal 226 with thepattern signal 728. The portion 800 of the echo signal 226 and theportion 802 of the pattern signal 728 are shown disposed above eachother and above a horizontal axis 804 that is representative of time. Anoutput signal 806 represents the signal that is output from thecomparison device 720. The output signal 806 represents differences(e.g., a time lag, amount of overlap, or other measure) between theportion 800 of the echo signal 226 and the portion 802 of the patternsignal 728. The comparison device 720 may output a single ended outputsignal 806 or a differential signal as the output signal 806 (havingcomponents 806A and 806B, as shown in FIG. 8).

In one embodiment, the comparison device 720 generates the output signal806 based on differences between the portion 800 of the echo signal 226and the portion 802 of the time-delayed pattern signal 728. For example,when a magnitude or amplitude of both portions 800, 802 is “high” (e.g.,has a positive value) or when the magnitude or amplitude of bothportions 800, 802 is “low” (e.g., has a zero or negative value), thecomparison device 720 may generate the output signal 806 to have a firstvalue. In the illustrated example, this first value is zero. When amagnitude or amplitude of both portions 800, 802 differ (e.g., one has ahigh value and the other has a zero or low value), the comparison device720 may generate the output signal 806 with a second value, such as ahigh value.

In the example of FIG. 8, the portion 800 of the echo signal 226 and theportion 802 of the pattern signal 728 have the same or similar valueexcept for time periods 808, 810. During these time periods 808, 810,the comparison device 720 generates the output signal 806 to have a“high” value. Each of these time periods 808, 810 can represent the timelag, or delay, between the portions 800, 802. During other time periods,the comparison device 720 generates the output signal 806 to have adifferent value, such as a “low” or zero value, as shown in FIG. 8.Similar output signals 806 may be generated for other portions of theecho signal 226 and pattern signal 728.

FIG. 9 illustrates another example of how the comparison device 720compares a portion 900 of the baseband echo signal 226 with a portion902 of the pattern signal 728. The portions 900, 902 have the same orsimilar values except for time periods 904, 906. During these timeperiods 904, 906, the comparison device 720 generates the output signal806 to have a “high” value. During other time periods, the comparisondevice 720 generates the output signal 806 to have a different value,such as a “low” or zero value. As described above, the comparison device720 may compare additional portions of the baseband signal 226 with thepattern signal 728 to generate additional portions or waveforms in theoutput signal 806.

FIG. 10 illustrates another example of how the comparison device 720compares a portion 1000 of the baseband echo signal 226 with a portion1002 of the pattern signal 230. The portions 1000, 1002 have the same orsimilar values over the time shown in FIG. 10. As a result, the outputsignal 806 that is generated by the comparison device 720 does notinclude any “high” values that represent differences in the portions1000, 1002. As described above, the comparison device 720 may compareadditional portions of the baseband signal 226 with the pattern signal728 to generate additional portions or waveforms in the output signal806. The output signals 806 shown in FIGS. 8, 9, and 10 are providedmerely as examples and are not intended to be limitations on allembodiments disclosed herein.

The output signals 806 generated by the comparison device 720 representtemporal misalignment between the baseband echo signal 226 and thepattern signal 728 that is delayed by the time of flight or time delaymeasured by the coarse stage determination. The temporal misalignmentmay be an additional portion (e.g., to be added to) the time of flightof the transmitted signals 106 (shown in FIG. 1) and the echoes 108(shown in FIG. 1) to determine the separation distance 110 (shown inFIG. 1).

The temporal misalignment between the baseband signal 226 and thepattern signal 728 may be referred to as a time lag. The time lag can berepresented by the time periods 808, 810, 904, 906. For example, thetime lag of the data stream 226 in FIG. 8 may be the time encompassed bythe time period 808 or 810, or the time by which the portion 802 of thebaseband signal 226 follows behind (e.g., lags) the portion 800 of thepattern signal 728. Similarly, the time lag of the portion 902 of thebaseband signal 226 may be the time period 904 or 906. With respect tothe example shown in FIG. 10, the portion 1000 of the baseband signaldoes not lag behind the portion 1002 of the pattern signal 728. Asdescribed above, several time lags may be measured by comparing more ofthe baseband signal 226 with the time-delayed pattern signal 728.

In order to measure the temporal misalignment between the basebandsignal 226 and the time-delayed pattern signal, the output signals 806may be communicated from the conversion device 720 to one or morefilters 722. In one embodiment, the filters 722 are low-pass filters.The filters 722 generate energy signals 724 that are proportional to theenergy of the output signals 806. The energy of the output signals 806is represented by the size (e.g., width) of waveforms 812, 910 in theoutput signals 806. As the temporal misalignment between the basebandsignal 226 and the pattern signal 728 increases, the size (and energy)of the waveforms 812, 910 increases. As a result, the amplitude and/orenergy conveyed or communicated by the energy signals 724 increases.Conversely, as the temporal misalignment between the baseband signal 226and the time-delayed pattern signal 728 decreases, the size and/oramplitude and/or energy of the waveforms 812, 910 also decreases. As aresult, the energy conveyed or communicated by the energy signals 724decreases.

As another example, the above system could be implemented using theopposite polarity, such as with an XNOR comparison device that produces“high” signals when the baseband signal 226 and the time-delayed patternsignal 728 are the same and “low” when they are different. In thisexample, as the temporal misalignment between the baseband signal 226and the pattern signal 728 increases, the size (and energy) of thewaveforms 812, 910 decreases. As a result, the amplitude and/or energyconveyed or communicated by the energy signals 724 decreases.Conversely, as the temporal misalignment between the baseband signal 226and the time-delayed pattern signal 728 decreases, the size, amplitude,and/or energy of the waveforms 812, 910 also increases. As a result, theenergy conveyed or communicated by the energy signals 724 increases.

The energy signals 724 may be communicated to measurement devices 726(“ADC” in FIG. 7). The measurement devices 726 can measure the energiesof the energy signals 724. The measured energies can then be used todetermine the additional portion of the time of flight that isrepresented by the temporal misalignment between the baseband signal 226and the time-delayed pattern signal 728. In one embodiment, themeasurement device 726 periodically samples the energy and/or amplitudeof energy signals 724 in order to measure the energies of the energysignals 724. For example, the measurement devices 726 may include orrepresent analog-to-digital converters (ADC) that sample the amplitudeand/or energy of the energy signals 724 in order to measure or estimatethe alignment (or misalignment) between the echo signal 226 and thepattern signal 728. The sampled energies can be communicated by themeasurement devices 726 as the output signal 702 to the control unit 112or other output device or component (shown as “Digital energy estimatesfor I or Q channel” in FIG. 7).

The control unit 112 (or other component that receives the output signal710) may examine the measured energy of the energy signals 724 andcalculate the additional portion of the time of flight represented bythe temporal misalignment between the baseband signal 226 and thetime-delayed pattern signal 728. The control unit 112 also may calculatethe additional portion of the separation distance 110 that is associatedwith the temporal misalignment. In one embodiment, the control unit 112compares the measured energy to one or more energy thresholds. Thedifferent energy thresholds may be associated with different amounts oftemporal misalignment. Based on the comparison, a temporal misalignmentcan be identified and added to the time of flight calculated using thecoarse stage determination described above. The separation distance 110may then be calculated based on the combination of the coarse stagedetermination of the time of flight and the additional portion of thetime of flight from the fine stage determination.

FIG. 11 illustrates examples of output signals 724 provided to themeasurement devices 726 and energy thresholds used by the control unit112 or other component or device (shown in FIG. 2) in accordance withone example. The output signals 702 are shown alongside a horizontalaxis 1102 representative of time and a vertical axis 1104 representativeof energy. Several energy thresholds 1106 are shown above the horizontalaxis 1102. Although eight output signals 724A-H and eight energythresholds 1106A-H are shown, alternatively, a different number ofoutput signals 724 and/or energy thresholds 1106 may be used.

The measurement devices 726 may digitize the energy signals 724 toproduce the energy data output signals 702. When the output signals 702are received from the measurement devices 726 (shown in FIG. 7) by theCPU 270, the output signals 706 can be compared to the energy thresholds1106 to determine which, if any, of the energy thresholds 1106 areexceeded by the output signals 702. For example, the output signals 702having less energy (e.g., a lower magnitude) than the energiesassociated with the output signal 702A may not exceed any of thethresholds 1106, while the output signal 702A approaches or reaches thethreshold 1106A. The output signal 702B is determined to exceed thethreshold 1106A, but not exceed the threshold 1106B. As shown in FIG.11, other output signals 702 may exceed some thresholds 1106 while notexceeding other thresholds 1106.

The different energy thresholds 1106 are associated with differenttemporal misalignments between the echo signal 226 and the time-delayedpattern signal 728 in one embodiment. For example, the energy threshold1106A may represent a temporal misalignment of 100 picoseconds, theenergy threshold 1106B may represent a temporal misalignment of 150picoseconds, the energy threshold 1106C may represent a temporalmisalignment of 200 picoseconds, the energy threshold 1106D mayrepresent a temporal misalignment of 250 picoseconds, and so on. Forexample, 724B may be the result of the situation shown in FIGS. 8 and724E may be the result of the situation in FIG. 9.

The measured energy of the output signal 702 can be compared to thethresholds 1106 to determine if the measured energy exceeds one or moreof the thresholds 1106. The temporal misalignment associated with thelargest threshold 1106 that is approached or reached or represented bythe energy of the output signal 702 may be identified as the temporalmisalignment between the echo signal 226 and the time-delayed patternsignal 728. In one embodiment, no temporal alignment may be identifiedfor output signals 702 having or representing energies that are lessthan the threshold 1106A.

The energy thresholds 1106 may be established by positioning targetobjects 104 (shown in FIG. 1) a known separation distance 110 (shown inFIG. 1) from the sensing assembly 102 (shown in FIG. 1) and observingthe levels of energy that are represented or reached or approached bythe output signals 702.

In addition or as an alternate to performing the fine stagedetermination of the time of flight, the ultrafine stage may be used torefine (e.g., increase the resolution of) the time of flightmeasurement, track movement, and/or detect movement of the target object104 (shown in FIG. 1). In one embodiment, the ultrafine stage includescomparing different components or channels of the same or different echosignals 226 as the fine stage determination. For example, in oneembodiment, the coarse stage determination may measure a time of flightfrom echo signals 226 that are based on echoes 108 received fromtransmission of a first set or burst of one or more transmitted signals106, as described above. The fine stage determination may measure anamount of temporal misalignment or overlap between echo signals 226 thatare based on echoes 108 received from transmission of a subsequent,second set or burst of one or more transmitted signals 106 (that may usethe same or different transmit pattern as the first set or burst oftransmitted signals 106). The fine stage determination may measure thetemporal misalignment between the echo signals 226 from the second setor burst of transmitted signals 106 and a receive pattern signal (whichmay be the same or different receive pattern as used by the coarse stagedetermination) as that is time delayed by the time of flight measured bythe coarse stage, as described above. In one embodiment, the fine stagedetermination examines the I and/or Q component or channel of the echosignals 226. The ultrafine stage determination may measure the temporalmisalignment of the echo signals 226 from the same second set or burstof transmitted signals 106 as the fine stage determination, or from asubsequent third set or burst of transmitted signals 106. The ultrafinestage determination may measure the temporal misalignment between theecho signals 226 and a receive pattern signal (that is the same ordifferent as the receive pattern signal used by the fine stagedetermination) that is time-delayed by the time of flight measured bythe coarse stage. In one embodiment, the ultrafine stage measures thetemporal misalignment of the I and/or Q component or channel of the echosignals 226 while the fine stage measures the temporal misalignment ofthe Q and/or I component or channel of the same or different echosignals 226. The temporal misalignment of the I component may becommunicated to the control unit 112 (or other component or device) asthe output signals 702 (as described above) while the temporalmisalignment of the Q component may be communicated to the control unit112 (or other component or device) as output signals 1228. Alternativelyor additionally, the time lag of the waveforms in the I channel and Qchannel can be examined to resolve phases of the echoes in order tocalculate separation distance or motion of the target.

As described above, the ultrafine stage determination may alternativelyor additionally involve a similar process as the coarse stagedetermination. For example, the coarse stage determination may examinethe I channel of the receive pattern and the data stream to determinecorrelation values of different subsets of the data stream and, fromthose correlation values, determine a subset of interest and acorresponding time-of-flight, as described herein. The ultrafine stagedetermination can use the Q channel of the receive pattern and the datastream to determine correlation values of different subsets of the datastream and, from those correlation values, determine a subset ofinterest and a time-of-flight. The times-of-flight from the I channeland Q channel can be combined (e.g., averaged) to calculate a time offlight and/or separation distance to the target. The correlation valuescalculated by the ultrafine stage determination can be used to calculatean additional time delay that can be added to the time delays from thecoarse stage and/or the fine stage to determine a time of flight and/orseparation distance to the target. Alternatively or additionally, thecorrelation values of the waveforms in the I channel and Q channel canbe examined to resolve phases of the echoes in order to calculateseparation distance or motion of the target.

FIG. 12 is a circuit diagram of another embodiment of a basebandprocessing system 1200 of the system 100 shown in FIG. 1. In oneembodiment, the baseband processing system 1200 is similar to thebaseband processing system 232 (shown in FIG. 7). For example, thebaseband processing system 1200 may be included in the sensing assembly102 (shown in FIG. 1) by being coupled with the front end receiver 218,the pattern code generator 228, and/or the baseband processor 232 of thesensing assembly 102. The baseband processing system 1200 includes twoor more parallel paths 1202, 1204 that the I and Q components of thebaseband echo signal 226 and the pattern signal can flow through forprocessing and analysis. For example, a first path 1202 can process andanalyze the I components of the echo signal 224 and baseband echo signal226 and the second path 1204 can process and analyze the Q components ofthe echo signal 224 and the baseband echo signal 226. In the illustratedembodiment, each of the paths 1202, 1204 includes the basebandprocessing system 232 described above. Alternatively, one or more of thepaths 1202, 1204 may include one or more other components for processingand/or analyzing the signals. In another embodiment, only a single path1202 or 1204 may process and/or analyze multiple, different componentsof the baseband echo signal 224 and/or baseband echo signal 226. Forexample, the path 1202 may examine the I component of the signal 224and/or 226 during a first time period and then examine the Q componentof the signal 224 and/or 226 during a different (e.g., subsequent orpreceding) second time period.

In operation, the echo signal 224 is received by the front end receiver218 and is separated into separate I and Q signals 1206, 1208 (alsoreferred to herein as I and Q channels). Each separate I and Q signal1206, 1208 includes the corresponding I or Q component of the echosignal 224 and can be processed and analyzed similar to the signalsdescribed above in connection with the baseband processing system 232shown in FIG. 7. For example, each of the I signal 1206 and the Q signal1208 can be received and/or amplified by a conversion amplifier 1210(that is similar to the conversion amplifier 704) in each path 1202,1204 to output a differential signal (e.g., similar to the signal 708shown in FIG. 7) to another amplifier 1212 (e.g., similar to theamplifier 706 shown in FIG. 7). The amplifiers 1212 can produce signalshaving increased gain (e.g., similar to the signals 710 shown in FIG. 7)that are provided to switch devices 1214. The switch devices 1214 can besimilar to the switch device 712 (shown in FIG. 7) and can communicatethe signals from the amplifiers 1212 to amplifiers 1216 (which may besimilar to the amplifier 714 shown in FIG. 7) and/or the correlatordevice 232 for the coarse stage identification of a time of flight, asdescribed above.

Similar to as described above in connection with the switch device 712(shown in FIG. 7), the switch devices 1214 can direct the signals fromthe amplifiers 1212 to comparison devices 1218 (that may be similar tothe comparison device 720 shown in FIG. 7), filters 1220 (that may besimilar to the filters 722 shown in FIG. 7), and measurement devices1222 (that may be similar to the measurement devices 726 shown in FIG.7). The comparison devices 1218 may each receive different components ofa receive pattern signal from the pattern code generator 228. Forexample, the comparison device 1218 in the first path 1202 may receivean I component 1224 of a receive pattern signal for the fine stage andthe comparison device 1218 in the second path 1202 may receive the Qcomponent 1226 of the receive pattern signal for the ultrafine stage.The comparison devices 1218 generate output signals that representtemporal misalignments between the I or Q components 1224, 1226 of thereceive pattern signal and the I or Q components of the echo signal 226,similar to as described above. For example, the comparison device 1218in the first path 1202 may output a signal having an energy thatrepresents (e.g., is proportional to) the temporal misalignment betweenthe I component of the baseband echo signal 226 and the I component ofthe time-delayed receive pattern signal 728. The comparison device 1218in the second path 1204 may output another signal having an energy thatrepresents the temporal misalignment between the Q component of thebaseband echo signal 226 and the Q component of the time-delayed patternsignal 728. Alternatively, there may be a single path 700, as shown inFIG. 7, that may be shared between I and Q operation. This could beaccomplished by alternately providing or switching between the I and Qcomponents of the baseband echo signal 226A ad 226B.

As described above, the energies of the signals output from thecomparison devices 1218 can pass through the filters 1220 and bemeasured by the measurement devices 1222 to determine each of thetemporal misalignments associated with the I and Q components of theecho signal 226 and the receive pattern signal. These temporalmisalignments can be added together and added to the time of flightdetermined by the coarse stage determination. The sum of the temporalmisalignments and the time of flight from the coarse stage determinationcan be used by the baseband processor 232 to calculate the separationdistance 110 (shown in FIG. 1), as described above. Because the I and Qcomponents of the echo signal and the time-delayed receive patternsignal are phase shifted by approximately 90 degrees from each other,separately examining the I and Q components allows calculation of thecarrier phase of the returning signal 108 according to Equation 2 belowand can provide resolution on the order of one eighth or better(smaller) of the wavelength of the carrier signal of the transmittedsignals 106 and echoes 108. Alternatively, there may be 3 or morecomponents separated by an amount other than 90 degrees.

In one embodiment, the ultrafine stage determination described above canbe used to determine relatively small movements that change theseparation distance 110 (shown in FIG. 1). For example, the ultrafinestage may be used to identify relatively small movements within aportion of the separation distance 110 that is associated with thesubset of interest in the baseband echo signal 226.

FIG. 13 illustrates projections of I and Q components of the basebandecho signal 226 in accordance with one embodiment. The ultrafine stagedetermination can include the baseband processor 232 (shown in FIG. 2)projecting a characteristic of the I and Q components of the basebandecho signal 226 onto a vector. As shown in FIG. 13, a vector 1300 isshown alongside a horizontal axis 1302 and a vertical axis 1304. Thebackend 202 or control unit 112 or other processing or computationdevices by examination of the data signals 234, 702, 1228, 260, orothers or a combination of some or all of the signals may determine thevector 1300 as a projection of the characteristic (e.g., amplitude) ofthe I component 1320 of the echo signal along the horizontal axis 1302and a projection of the characteristic (e.g., amplitude) of the Qcomponent 1321 of the echo signal along the vertical axis 1304. Forexample, the vector 1300 may extend to a location along the horizontalaxis 1302 by an amount that is representative of an amplitude of the Icomponent of the echo signal and to a location along the vertical axis1304 by an amount that is representative of an amplitude of the Qcomponent of the echo signal. The phase of the carrier can thencalculated as:

$\begin{matrix}{\varphi = {\arctan\left( \frac{I}{Q} \right)}} & \left( {{Equation}\mspace{14mu}{\# 2}} \right)\end{matrix}$where φ denotes the phase and I is the I projection 1320 and Q is the Qprojection 1321. The carrier phase or the change in carrier phase can beused to calculate the distance or change in distance through theequation:

$\begin{matrix}{{distance} = \frac{\varphi \times \lambda}{360}} & \left( {{Equation}\mspace{14mu}{\# 3}} \right)\end{matrix}$where λ is the wavelength of the carrier frequency and φ is the phaseexpressed in degrees as calculated from Equation 2 above.

The baseband processor 232 (shown in FIG. 2) may then determineadditional vectors 1306, 1308 based on the echoes 108 (shown in FIG. 1)received from additional transmitted signals 106 (shown in FIG. 1).Based on changes in the vector 1300 to the vector 1306 or the vector1308, the baseband processor 232 may identify movement of the targetobject 104 (shown in FIG. 1) within the portion of the separationdistance 110 (shown in FIG. 1) that is associated with the subset ofinterest. For example, rotation of the vector 1300 in acounter-clockwise direction 1310 toward the location of the vector 1306may represent movement of the target object 104 toward the sensingassembly 102 shown in FIG. 1 (or movement of the sensing assembly 102toward the target object 104). Rotation of the vector 1300 in aclockwise direction 1312 toward the location of the vector 1308 mayrepresent movement of the target object 104 away from the sensingassembly 102 (or movement of the sensing assembly 102 toward the targetobject 104). Alternatively, movement of the vector 1300 in thecounter-clockwise direction 1310 may represent movement of the targetobject 104 away from the sensing assembly 102 (or movement of thesensing assembly 102 toward the target object 104) while movement of thevector 1300 in the clockwise direction 1312 may represent movement ofthe target object 104 toward the sensing assembly 102 shown in FIG. 1(or movement of the sensing assembly 102 toward the target object 104).The correlator device 232 may be calibrated by moving the target object104 toward and away from the sensing assembly 102 to determine whichdirection of movement results in rotation of the vector 1300 in theclockwise direction 1312 or counter-clockwise direction 1310.

The coarse, fine, and/or ultrafine stage determinations described abovemay be used in a variety of combinations. For example, the coarse stagedetermination may be used to calculate the separation distance 110(shown in FIG. 1), even if the approximate distance from the sensingdevice 102 (shown in FIG. 1) to the target object 104 (shown in FIG. 1)is not known. Alternatively, the coarse stage may be used with the fineand/or ultrafine stage determinations to obtain a more precisecalculation of the separation distance 110. The coarse, fine andultrafine stages may be used in any combination at different times inorder to balance various performance metrics.

As another example, if the separation distance 110 (shown in FIG. 1) isknown, the fine or ultrafine stage determinations can be activatedwithout the need for first identifying the bit of interest using thecoarse stage determination. For example, the system 100 (shown inFIG. 1) may be in a “tracking” mode where updates from the initial knownseparation distance 110 are identified and/or recorded using the fineand/or ultrafine state determinations.

Returning to the discussion of the system 100 shown in FIG. 1, inanother embodiment, the system 100 discern between echoes 108 that arereflected off of different target objects 104. For example, in some usesof the system 100, the transmitted signals 106 may reflect off ofmultiple target objects 104. If the target objects 104 are locateddifferent separation distances 110 from the sensing assembly 102, asingle baseband echo signal 226 (shown in FIG. 2) may represent severalsequences of bits that represent echoes off the different target objects104. As described below, a mask may be applied to the baseband echosignal 226 and the pattern in the correlation window that is compared tothe baseband echo signal 226 in order to distinguish between thedifferent target objects 104.

FIG. 14 illustrates a technique for distinguishing between echoes 108(shown in FIG. 1) that are reflected off different target objects 104(shown in FIG. 1) in accordance with one embodiment. When a firsttransmitted signal 106 shown in FIG. 1 (or a series of first transmittedsignals 106) reflect off of multiple target objects 104, the digitalpulse sequence (e.g., the pattern of bits) in the pattern signal 230(shown in FIG. 2) may be modified relative to the digital pulse sequencein the first transmitted signal 106 for transmission of a secondtransmitted signal 106 (or series of second transmitted signals 106).The echoes 108 and corresponding baseband echo signal 226 (shown in FIG.2) of the second transmitted signal 106 may be compared to the modifieddigital pulse sequence to distinguish between the multiple targetobjects 104 (e.g., to calculate different times of flight and/orseparation distances 110 associated with the different target objects104).

A first digitized echo signal 1400 in FIG. 14 represents the sequence ofbits that may be generated when a transmitted signal 106 (shown inFIG. 1) reflects off a first target object 104 at a first separationdistance 110 (shown in FIG. 1) from the sensing assembly 102 (shown inFIG. 1). A second digitized echo signal 1402 represents the sequence ofbits that may be generated when the transmitted signal 106 reflects offa different, second target object 104 that is a different, secondseparation distance 110 from the sensing assembly 102. Instead ofseparately generating the digitized echo signals 1400, 1402, the sensingassembly 102 may generate a combined digitized echo signal 1404 thatrepresents the combination of echoes 108 off the different targetobjects 104. The combined digitized echo signal 1404 may represent acombination of the digitized echo signals 1400, 1402.

A correlation window 1406 includes a sequence 1414 of bits that can becompared to either digitized echo signal 1400, 1402 to determine asubset of interest, such as the subsets of interest 1408, 1410, in orderto determine times of flight to the respective target objects 104 (shownin FIG. 1), as described above. However, when the echoes 108 (shown inFIG. 1) off the target objects 104 are combined and the combineddigitized echo signal 1404 is generated, the correlation window 1406 maybe less accurate or unable to determine the time of flight to one ormore of the several target objects 104. For example, while separatecomparison of the correlation window 1406 to each of the digitized echosignals 1400, 1402 may result in correlation values of +6 beingcalculated for the subsets of interest 1408, 1410, comparison of thecorrelation window 1406 to the combined digitized echo signal 1404 mayresult in correlation values of +5, +4, and +4 for the subsets thatinclude the first through sixth bits, the third through eighth bits, andthe seventh through twelfth bits in the combined digitized echo signal1404. As a result, the baseband processor 232 (shown in FIG. 2) may beunable to distinguish between the different target objects 104 (shown inFIG. 1).

In one embodiment, a mask 1412 can be applied to the sequence 1414 ofbits in the correlation window 1406 to modify the sequence 1414 of bitsin the correlation window 1406. The mask 1412 can eliminate or otherwisechange the value of one or more of the bits in the correlation window1406. The mask 1412 can include a sequence 1416 of bits that are appliedto the correlation window 1406 (e.g., by multiplying the values of thebits) to create a modified correlation window 1418 having a sequence1420 of bits that differs from the sequence 1414 of bits in thecorrelation window 1406. In the illustrated example, the mask 1412includes a first portion of the first three bits (“101”) and a secondportion of the last three bits (“000”). Alternatively, another mask 1412may be used that has a different sequence of bits and/or a differentlength of the sequence of bits. Applying the mask 1412 to thecorrelation window 1406 eliminates the last three bits (“011”) in thesequence 1414 of bits in the correlation window 1406. As a result, thesequence 1420 of bits in the modified correlation window 1418 includesonly the first three bits (“101”) of the correlation window 1418. Inanother embodiment, the mask 1412 adds additional bits to thecorrelation window 1406 and/or changes values of the bits in thecorrelation window 1406.

The sequence 1420 of bits in the modified correlation window 1418 can beused to change the sequence of bits in the pattern signal 230 (shown inFIG. 2) that is communicated to the transmitter for inclusion in thetransmitted signals 106 (shown in FIG. 1). For example, after receivingthe combined digitized echo signal 1404 and being unable to discernbetween the different target objects 104 (shown in FIG. 1), the sequenceof bits in the pattern that is transmitted toward the target objects 104can be changed to include the sequence 1420 of bits in the modifiedcorrelation window 1412 or some other sequence of bits to aid in thediscernment of the different target objects 104. An additional combineddigitized echo signal 1422 may be received based on the echoes 108 ofthe transmitted signals 106 that include the sequence 1420 of bits.

The modified correlation window 1418 can then be compared with theadditional digitized echo signal 1422 to identify subsets of interestassociated with the different target objects 104 (shown in FIG. 1). Inthe illustrated embodiment, the modified correlation window 1418 can becompared to different subsets of the digitized echo signal 1422 toidentify first and second subsets of interest 1424, 1426, as describedabove. For example, the first and second subsets of interest 1424, 1426may be identified as having higher or the highest correlation valuesrelative to other subsets of the digitized echo signal 1422.

In operation, when transmitted signals 106 reflect off multiple targetobjects 104, the pattern transmitted in the signals 106 can be modifiedrelatively quickly between successive bursts of the transmitted signals106 when one or more of the target objects 104 cannot be identified fromexamination of the digitized echo signal 226. The modified pattern canthen be used to distinguish between the target objects 104 in thedigitized echo signal 740 using the correlation window that includes themodified pattern.

In another embodiment, the digital pulse sequence of bits included in atransmitted signal 106 (shown in FIG. 1) may be different from thedigital pulse sequence of bits included in the correlation window andcompared to the baseband echo signal 226 (shown in FIG. 2). For example,the pattern code generator 228 (shown in FIG. 2) may createheterogeneous patterns and communicate the heterogeneous patterns in thepattern signals 230 (shown in FIG. 2) to the transmitter 208 and thebaseband processor 232. The transmitter 208 can mix a first pattern ofbits in the transmitted signal 106 and the baseband processor 232 cancompare a different, second pattern of bits to the baseband echo signal226 that is generated based on echoes 108 (shown in FIG. 1) of thetransmitted signals 106. With respect to the example described above inconnection with FIG. 14, the sequence 1414 of bits in the correlationwindow 1406 can be included in the transmitted signals 106 while thesequence 1416 of bits in the mask 1412 or the sequence 1420 of bits inthe modified correlation window 1418 can be compared to the digitizedecho signal 1422. Using different patterns in this manner can allow forthe sensing assembly 102 (shown in FIG. 1) to distinguish betweenmultiple target objects 104, as described above. Using differentpatterns in this manner can additionally allow for the sensing assembly102 (shown in FIG. 1) to perform other functions including, but notlimited to clutter mitigation, signal-to-noise improvement,anti-jamming, anti-spoofing, anti-eavesdropping, and others.

FIG. 15 is a schematic view of an antenna 1500 in accordance with oneembodiment. The antenna 1500 may be used as the transmitting antenna 204and/or the receiving antenna 206, both of which are shown in FIG. 2.Alternatively, another antenna may be used for the transmitting antenna204 and/or the receiving antenna 206. The antenna 1500 includes amulti-dimensional (e.g., two dimensional) array 1502 of antenna unitcells 1504. The unit cells 1504 may represent or include microstrippatch antennas. Alternatively, the unit cells 1504 may represent anothertype of antenna. Several unit cells 1504 can be conductively coupled inseries with each other to form a series-fed array 1506. In theillustrated embodiment, the unit cells 1504 are connected in a linearseries. Alternatively, the unit cells 1504 can be connected in anothershape.

Several series-fed arrays 1506 are conductively coupled in parallel toform the array 1502 in the illustrated embodiment. The numbers of unitcells 1504 and series-fed arrays 1506 shown in FIG. 15 are provided asexamples. A different number of unit cells 1504 and/or arrays 1506 maybe included in the antenna 1500. The antenna 1500 may use the severalunit cells 1504 to focus the energy of the transmitted signals 106(shown in FIG. 1) through constructive and/or destructive interference.

FIG. 16 is a schematic diagram of one embodiment of the front end 200 ofthe sensing assembly 102 (shown in FIG. 1). The antennas 1500 may beused as the transmitting antenna 204 and the receiving antenna 206, asshown in FIG. 16. Each antenna 1500 may be directly connected to thereceiver 602 or transmitter 600 (e.g., with no other components disposedbetween the antenna 1500 and the receiver 602 or transmitter 600) by arelatively short length of transmission line 1600.

The front end 200 of the sensing assembly 102 may be housed in anenclosure 1602, such as a metal or otherwise conductive housing, withradio transmissive windows 1604 over the antennas 1500. Alternatively,the front end 200 may be housed in a non-metallic (e.g., dielectric)enclosure. The windows over the antennas 1500 may not be cut out of theenclosure 1602, but may instead represent portions of the enclosure 1602that allows the transmitted signals 106 and echoes 108 pass through thewindows 1604 from or to the antennas 1500.

The enclosure 1602 may wrap around the antennas 1500 so that theantennas are effectively recessed into the conducting body of theenclosure 1602, which can further improve isolation between the antennas1500. Alternatively, in the case of a non-conducting enclosure 1602, theantennas 1500 may be completely enclosed by the enclosure 1602 and extrametal foil, and/or absorptive materials, or other measures may be addedto improve isolation between the antennas 1500. In one embodiment, ifthe isolation is sufficiently high, the transmit and receiving antennas1500 can be operated at the same time if the returning echoes 108 aresufficiently strong. This may be the case when the target is at veryclose range, and can allow for the sensing assembly 102 to operatewithout a transmit/receive switch.

FIG. 17 is a cross-sectional view of one embodiment of the antenna 1500along line 17-17 in FIG. 16. The antenna 1500 (“Planar Antenna” in FIG.17) includes a cover layer 1700 (“Superstrate” in FIG. 17) of anelectrically insulating material (such as a dielectric or othernonconducting material). Examples of such materials for the cover layer1700 include, but are not limited to quartz, sapphire, various polymers,and the like.

The antenna 1500 may be positioned on a surface of a substrate 1706 thatsupports the antenna 1500. A conductive ground plane 1708 may bedisposed on an opposite surface of the substrate 1706, or in anotherlocation.

The cover layer 1700 may be separated from the antenna 1500 by an airgap 1704 (“Air” in FIG. 17). Alternatively, gap between the cover layer1700 and the antenna 1500 may be at least partially filled by anothermaterial or fluid other than air. As another alternative, the air gapmay be eliminated, and the cover layer 1700 may rest directly on theantenna 1500. The cover layer 1700 can protect the antenna 1500 from theenvironment and/or mechanical damage caused by external objects. In oneembodiment, the cover layer 1700 provides a lensing effect to focus theenergy of the transmitted signals 106 emitted by the antenna 1500 into abeam or to focus the energy of the reflected echoes 108 toward theantenna 1500.

This lensing effect can permit transmitted signals 106 and/or echoes 108to pass through additional layers 1702 of materials (e.g., insulatorssuch as Teflon, polycarbonate, or other polymers) that are positionedbetween the antenna 1500 and the target object 104 (shown in FIG. 1).For example, the sensing assembly 102 can be mounted to an object beingmonitored (e.g., the top of a tank of fluid being measured by thesensing assembly 102), while the lensing effect can permit the sensingassembly 102 to transmit the signals 106 and receive the echoes 108through the top of the tank without cutting windows or openings throughthe top of the tank).

In one embodiment, the substrate 1708 may have a thickness dimensionbetween the opposite surfaces that is thinner than a wavelength of thecarrier signal of the transmitted signals 106 and/or echoes 108. Forexample, the thickness of the substrate 1708 may be on the order of1/20th of a wavelength. The thicknesses of the air gap 1704 and/orsuperstrate 1700 may be larger, such as ⅓ of the wavelength. Either oneor both of the air gap 1704 and the superstrate 1700 may also be removedaltogether.

One or more embodiments of the system 100 and/or sensing assembly 102described herein may be used for a variety of applications that use theseparation distance 110 and/or time of flight that is measured by thesensing assembly 102. Several specific examples of applications of thesystem 100 and/or sensing assembly 102 are described herein, but not allapplications or uses of the system 100 or sensing assembly 102 arelimited to those set forth herein. For example, many applications thatuse the detection of the separation distance 110 (e.g., as a depthmeasurement) can use or incorporate the system 100 and/or sensingassembly 102.

FIG. 18 illustrates one embodiment of a containment system 1800. Thesystem 1800 includes a containment apparatus 1802, such as a fluid tank,that holds or stores one or more fluids 1806. The sensing assembly 102may be positioned on or at a top 1804 of the containment apparatus 1802and direct transmitted signals 106 toward the fluid 1806. Reflectedechoes 108 from the fluid 1806 are received by the sensing assembly 102to measure the separation distance 110 between the sensing assembly 102and an upper surface of the fluid 1806. The location of the sensingassembly 102 may be known and calibrated to the bottom of thecontainment apparatus 1802 so that the separation distance 110 to thefluid 1806 may be used to determine how much fluid 1806 is in thecontainment apparatus 1802. The sensing assembly 102 may be able toaccurately measure the separation distance 110 using one or more of thecoarse, fine, and/or ultrafine stage determination techniques describedherein.

Alternatively or additionally, the sensing apparatus 102 may directtransmitted signals 106 toward a port (e.g., a filling port throughwhich fluid 1806 is loaded into the containment apparatus 1802) andmonitor movement of the fluid 1806 at or near the port. For example, ifthe separation distance 110 from the sensing assembly 102 to the port isknown such that the bit of interest of the echoes 108 is known, theultrafine stage determination described above maybe used to determine ifthe fluid 1806 at or near the port is moving (e.g., turbulent). Thismovement may indicate that fluid 1806 is flowing into or out of thecontainment apparatus 1802. The sensing assembly 102 can use thisdetermination as an alarm or other indicator of when fluid 1806 isflowing into or out of the containment apparatus 1802. Alternatively,the sensing assembly 102 could be positioned or aimed at otherstrategically important locations where the presence or absence ofturbulence and/or the intensity (e.g., degree or amount of movement)could indicate various operating conditions and parameters (e.g.,amounts of fluid, movement of fluid, and the like). The sensing assembly102 could periodically switch between these measurement modes (e.g.,measuring the separation distance 110 being one mode and monitoring formovement being another mode), and then report the data and measurementsto the control unit 112 (shown in FIG. 1). Alternatively, the controlunit 112 could direct the sensing assembly 102 to make the various typesof measurements (e.g., measuring the separation distance 110 ormonitoring for movement) at different times.

FIG. 19 illustrates one embodiment of a zone restriction system 1900.The system 1900 may include a sensing assembly 102 directing transmittedsignals 106 (shown in FIG. 1) toward a first zone 1902 (e.g., area on afloor, volume in space, and the like). A human operator 1906 may belocated in a different, second zone 1904 to perform various duties. Thefirst zone 1902 may represent a restricted area or volume where theoperator 1906 is to remain out of when one or more machines (e.g.,automated robots or other components) operate for the safety of theoperator 1906. The sensing assembly 102 can direct the transmittedsignals 106 toward the first zone 1902 and monitor the received echoes108 to determine if the operator 1906 enters into the first zone 1902.For example, intrusion of the operator 1906 into the first zone 1902 maybe detected by identification of movement using the one or more of thecoarse, fine, and/or ultrafine stage determination techniques describedherein. If the sensing assembly 102 knows the distance to the first zone1902 (e.g., the separation distance 110 to the floor in the first zone1902), then the sensing assembly 102 can monitor for movement within thesubset of interest in the echo signal that is generated based on theechoes, as described above. When the sensing assembly 102 detects entryof the operator 1906 into the first zone 1902, the sensing assembly 102can notify the control unit 112 (shown in FIG. 1), which can deactivatemachinery operating in the vicinity of the first zone 1902 to avoidinjuring the operator 1906.

FIG. 20 illustrates another embodiment of a volume restriction system2000. The system 2000 may include a sensing assembly 102 directingtransmitted signals 106 (shown in FIG. 1) toward a safety volume 2002(“Safety zone” in FIG. 20). Machinery 2004, such as an automated ormanually control robotic device, may be located and configured to movewithin the safety volume 2002. The volume through which the transmittedsignals 106 are communicated may be referred to as a protected volume2006. The protected zone 2006 may represent a restricted area or volumewhere humans or other objects are to remain out of when the machinery2004 operates. The sensing assembly 102 can direct the transmittedsignals 106 through the protected volume 2006 and monitor the receivedechoes 108 to determine if there is any motion identified outside of thesafety zone 2002 but within the protected zone 2006. For example,intrusion of a human into the protected volume 2006 may be detected byidentification of movement using the ultrafine stage determinationdescribed above. When the sensing assembly 102 detects entry into theprotected volume 2006, the sensing assembly 102 can notify the controlunit 112 (shown in FIG. 1), which can deactivate the machinery 2004 toavoid injuring any person or thing that has entered into the protectedvolume 2006.

FIG. 21 is a schematic diagram of one embodiment of a mobile system 2100that includes the sensing assembly 102. The system 2100 includes amobile apparatus 2102 with the sensing assembly 102 coupled thereto. Inthe illustrated embodiment, the mobile apparatus 2102 is a mobilizedrobotic system. Alternatively, the mobile apparatus 2102 may representanother type of mobile device, such as an automobile, an undergrounddrilling vessel, or another type of vehicle. The system 2100 usesmeasurements made by the sensing assembly 102 to navigate around orthrough objects. The system 2100 may be useful for automated navigationbased on detection of motion and/or measurements of separation distances110 between the sensing assembly 102 and other objects, and/or fornavigation that is assisted with such measurements and detections.

For example, the sensing assembly 102 can measure separation distances110 between the sensing assembly 102 and multiple objects 2104A-D in thevicinity of the mobile apparatus 2102. The mobile apparatus 2102 can usethese separation distances 110 to determine how far the mobile apparatus2102 can travel before needing to turn or change direction to avoidcontact with the objects 2104A-D.

In one embodiment, the mobile apparatus 2102 can use multiple sensingassemblies 102 to determine a layout or map of an enclosed vicinity 2106around the mobile apparatus 2102. The vicinity 2106 may be bounded bythe walls of a room, building, tunnel, and the like. A first sensingassembly 102 on the mobile apparatus 2102 may be oriented to measureseparation distances 110 to one or more boundaries (e.g., walls orsurfaces) of the vicinity 2106 along a first direction, a second sensingassembly 102 may be oriented to measure separation distances 110 to oneor more other boundaries of the vicinity 2106 along a different (e.g.,orthogonal) direction, and the like. The separation distances 110 to theboundaries of the vicinity 2106 can provide the mobile apparatus 2102with information on the size of the vicinity 2106 and a current locationof the mobile apparatus 2102. The mobile apparatus 2102 may then move inthe vicinity 2106 while one or more of the sensing assemblies 102acquire updated separation distances 110 to one or more of theboundaries of the vicinity 2106. Based on changes in the separationdistances 110, the mobile apparatus 2102 may determine where the mobileapparatus 2102 is located in the vicinity 2106. For example, if aninitial separation distance 110 to a first wall of a room is measured asten feet (three meters) and an initial separation distance 110 to asecond wall of the room is measured as five feet (1.5 meters), themobile apparatus 2102 may initially locate itself within the room. If alater separation distance 110 to the first wall is four feet (1.2meters) and a later separation distance 110 to the second wall is sevenfeet (2.1 meters), then the mobile apparatus 2102 may determine that ithas moved six feet (1.8 meters) toward the first wall and two feet (0.6meters) toward the second wall.

In one embodiment, the mobile apparatus 2102 can use informationgenerated by the sensing assembly 102 to distinguish between immobileand mobile objects 2104 in the vicinity 2106. Some of the objects 2104A,2104B, and 2104D may be stationary objects, such as walls, furniture,and the like. Other objects 210C may be mobile objects, such as humanswalking through the vicinity 2106, other mobile apparatuses, and thelike. The mobile apparatus 2102 can track changes in separationdistances 110 between the mobile apparatus 2102 and the objects 2104A,2104B, 2104C, 2104D as the mobile apparatus 2102 moves. Because theseparation distances 110 between the mobile apparatus 2102 and theobjects 2104 may change as the mobile apparatus 2102 moves, both thestationary objects 2104A, 2104B, 2104D and the mobile objects 2104C mayappear to move to the mobile apparatus 2102. This perceived motion ofthe stationary objects 2104A, 2104B, 2104D that is observed by thesensing assembly 102 and the mobile apparatus 2102 is due to the motionof the sensing assembly 102 and the mobile apparatus 2102. To computethe motion (e.g., speed) of the mobile apparatus 2102, the mobileapparatus 210 can track changes in separation distances 110 to theobjects 2104 and generate object motion vectors associated with theobjects 2104 based on the changes in the separation distances 110.

FIG. 22 is a schematic diagram of several object motion vectorsgenerated based on changes in the separation distances 110 between themobile apparatus 2102 and the objects (e.g., the objects 2104 of FIG.21) in accordance with one example. The object motion vectors 2200A-Fcan be generated by tracking changes in the separation distances 110over time. In order to estimate motion characteristics (e.g., speedand/or heading) of the mobile apparatus 2102, these object motionvectors 2200 can be combined, such as by summing and/or averaging theobject motion vectors 2200. For example, a motion vector 2202 of themobile apparatus 2102 may be estimated by determining a vector that isan average of the object motion vectors 2200 and then determining anopposite vector as the motion vector 2202. The combining of severalobject motion vectors 2200 can tend to correct spurious object motionvectors that are due to other mobile objects in the environment, such asthe object motion vectors 2200C, 2200F that are based on movement ofother mobile objects in the vicinity.

The mobile apparatus 2102 can learn (e.g., store) which objects are partof the environment and that can be used for tracking movement of themobile apparatus 2102 and may be referred to as persistent objects.Other objects that are observed that do not agree with the knownpersistent objects are called transient objects. Object motion vectorsof the transient objects will have varying trajectories and may notagree well with each other or the persistent objects. The transientobjects can be identified by their trajectories as well as their radialdistance from the mobile apparatus 2102, e.g. the walls of the tunnelwill remain at their distance, whereas transient objects will passcloser to the mobile apparatus 2102.

In another embodiment, multiple mobile apparatuses 2102 may include thesensing system 100 and/or sensing assemblies 102 to communicateinformation between each other. For example, the mobile apparatuses 2102may each use the sensing assemblies 102 to detect when the mobileapparatuses 2102 are within a threshold distance from each other. Themobile apparatuses 2102 may then switch from transmitting thetransmitted signals 106 in order to measure separation distances 110and/or detect motion to transmitting the transmitted signals 106 tocommunicate other information. For example, instead of generating thedigital pulse sequence to measure separation distances 110, at least oneof the mobile apparatuses 2102 may use the binary code sequence (e.g.,of ones and zeros) in a pattern signal that is transmitted towardanother mobile apparatus 2102 to communicate information. The othermobile apparatus 2102 may receive the transmitted signal 106 in order toidentify the transmitted pattern signal and interpret the informationthat is encoded in the pattern signal.

FIG. 23 is a schematic diagram of one example of using the sensingassembly 102 in a medical application. The sensing assembly 102 may useone or more of the stages described above (e.g., coarse stage, finestage, and ultrafine stage) to monitor changes in position of a patient2300 and/or relatively small movements of the patient. For example, theultrafine stage determination of movement described above may be usedfor breath rate detection, heart rate detection, monitoring gross motoror muscle movement, and the like. Breath rate, heart rate and activitycan be useful for diagnosing sleep disorders, and since the sensing isnon-contact and can be more comfortable for the patient being observed.As one example, the separation distance 110 to the abdomen and/or chestof the patient 2300 can be determined to within one bit of the digitalpulse sequence (e.g., the bit of interest), as described above. Thesensing assembly 102 can then track relatively small motions of thechest and/or abdomen within the subset of interest to track a breathingrate and/or heart rate. Additionally or alternatively, the sensingassembly 102 can track the motions of the chest and/or abdomen andcombine the motions with a known, measured, observed, or designated sizeof the abdomen to estimate the tidal volume of breaths of the patient2300. Additionally or alternatively, the sensing assembly 102 can trackthe motions of the chest and abdomen together to detect paradoxicalbreathing of the patient 2300.

As another example, the sensing assembly 102 may communicate transmittedsignals 106 that penetrate into the body of the patient 2300 and sensethe motion or absolute position of various internal structures, such asthe heart. Many of these positions or motions can be relatively smalland subtle, and the sensing assembly 102 can use the ultrafine stagedetermination of motion or the separation distance 110 to sense themotion or absolute position of the internal structures.

Using the non-contact sensing assembly 102 also may be useful forsituations where it is impossible or inconvenient to use wired sensorson the patient 2300 (e.g., sensors mounted directly to the test subject,connected by wires back to a medical monitor). For example, inhigh-activity situations where conventional wired sensors may get in theway, the sensing assembly 102 may monitor the separation distance 110and/or motion of the patient 2300 from afar.

In another example, the sensing assembly 102 can be used for posturerecognition and overall motion or activity sensing. This can be used forlong-term observation of the patient 2300 for the diagnosis of chronicconditions, such as depression, fatigue, and overall health of at-riskindividuals such as the elderly, among others. In the case of diseaseswith relatively slow onset, such as depression, the long termobservation by the sensing assembly 102 may be used for early detectionof the diseases. Also, since the unit can detect the medical parametersor quantities without anything being mounted on the patient 2300, thesensing assembly 102 may be used to make measurements of the patient2300 without the knowledge or cooperation of the patient 2300. Thiscould be useful in many situations, such as when dealing with childrenwho would be made upset if sensors are attached to them. It may alsogive an indication of the mental state of a patient 2300, such as theirbreath becoming rapid and shallow when they become nervous. This wouldgive rise to a remote lie-detector functionality.

In another embodiment, data generated by the sensing assembly 102 may becombined with data generated or obtained by one or more other sensors.For example, calculation of the separation distance 110 by the sensingassembly 102 may be used as a depth measurement that is combined withother sensor data. Such combination of data from different sensors isreferred to herein as sensor fusion, and includes the fusing of two ormore separate streams of sensor data to form a more complete picture ofthe phenomena or object or environment that is being sensed.

As one example, separation distances 110 calculated using the sensingassembly 102 may be combined with two-dimensional image data acquired bya camera. For example, without the separation distances 110, a computeror other machine may not be able to determine the actual physical sizeof the objects in a two-dimensional image.

FIG. 24 is a two-dimensional image 2404 of human subjects 2400, 2402 inaccordance with one example of an application of the system 100 shown inFIG. 1. The image 2404 may be acquired by a two-dimensional imageforming apparatus, such as a camera. The image forming apparatus mayacquire the image for use by another system, such as a security system,an automatically controlled (e.g., moveable) robotic system, and thelike. The human subjects 2400, 2402 may be approximately the same size(e.g., height). In reality, the human subject 2400 is farther from theimage forming apparatus that acquired the image 2404 than the humansubject 2402. However, due to the inability of the image formingapparatus to determine the relative separation distances between theimage forming apparatus and each of the subjects 2400, 2402, the systemthat relies on the image forming apparatus to recognize the subjects2400, 2402 may be unable to determine if the subject 2400 is locatedfarther away (e.g., is at the location of 2400A) or is a much smallerhuman than the subject 2402 (e.g., is the size represented by 2400B).

The sensing assembly 102 (shown in FIG. 1) can determine separationdistances 110 (shown in FIG. 1) between the image forming apparatus(e.g., with the sensing assembly 102 disposed at or near the imageforming apparatus) and each of the subjects 2400, 2402 to provide adepth context to the image 2404. For example, the image formingapparatus or the system that uses the image 2404 for one or moreoperations may use the separation distance 110 to each of the subjects2400, 2402 to determine that the subjects 2400, 2402 are approximatelythe same size, with the subject 2400 located farther away than thesubject 2402.

With this separation distance 110 (shown in FIG. 1) information andinformation about the optics that were used to capture the twodimensional image 2400, it may be possible to assign actual physicalsizes to the subjects 2400, 2402. For example, knowing the physical sizethat is encompassed by different portions (e.g., pixels or groups ofpixels) of the image 2400 and knowing the separation distance 110 toeach subject 2400, 2402, the image forming apparatus and/or the systemusing the image 2404 for one or more operations can calculate sizes(e.g., heights and/or widths) of the subjects 2400, 2402.

FIG. 25 is a schematic diagram of a sensing system 2500 that may includethe sensing assembly 102 (shown in FIG. 1) in accordance with oneembodiment. Many types of sensors such as light level sensors, radiationsensors, moisture content sensors, and the like, obtain measurements oftarget objects 104 that may change as the separation distance 110between the sensors and the target objects 104 varies. The sensingsystems 2500 shown in FIG. 25 may include or represent one or moresensors that acquire information that changes as the separation distance110 changes and may include or represent the sensing assembly 102.Distance information (e.g., separation distances 110) from the sensingsystems 2500 and the target objects 104 can provide for calibration orcorrection of other sensor information that is dependent on the distancebetween the sensor and the targets being read or monitored by thesensor.

For example, the sensing systems 2500 can acquire or measure information(e.g., light levels, radiation, moisture, heat, and the like) from thetarget objects 104A, 104B and the separation distances 110A, 110B to thetarget objects 104A, 104B. The separation distances 110A, 110B can beused to correct or calibrate the measured information. For example, ifthe target objects 104A, 104B both provide the same light level,radiation, moisture, heat, and the like, the different separationdistances 110A, 110B may result in the sensing systems 2500A, 2500Bmeasuring different light levels, radiation, moisture, heat, and thelike. With the sensing assembly 102 (shown in FIG. 1) measuring theseparation distances 110A, 110B, the measured information for the targetobject 104A and/or 104B can be corrected (e.g., increased based on thesize of the separation distance 110A for the target object 104A and/ordecreased based on the size of the separation distance 110B for thetarget object 104B) so that the measured information is more accuraterelative to not correcting the measured information for the differentseparation distances 110.

As another example, the sensing system 2500 may include a reflectivepulse oximetry sensor and the sensing assembly 102. Two or moredifferent wavelengths of light are directed at the surface of the targetobject 104 by the system 2500 and a photo detector of the system 2500examines the scattered light. The ratio of the reflected power can beused to determine the oxygenation level of the blood in the targetobject 104. Instead of being directly mounted (e.g., engaged to) thebody of the patient that is the target object 104, the sensing system2500 may be spaced apart from the body of the patient.

The surface of the patient body can be illuminated with light sourcesand the sensing assembly 102 (shown in FIG. 1) can measure theseparation distance 110 to the target object 104 (e.g., to the surfaceof the skin) The oxygenation level of the blood in the patient can thenbe calibrated or corrected for the decrease in the reflected power ofthe light that is caused by the sensing system 2500 being separated fromthe patient.

In another embodiment, the sensing assembly 102 and/or system 100 shownin FIG. 1 can be provided as a stand-alone unit that can communicatewith other sensors, controllers, computers, and the like, to add theabove-described functionality to a variety of sensor systems. Asoftware-implemented system can collect and aggregate the informationstreams from the sensors and deliver the sensed information to thecontrolling system, where the separation distance 110 measured by theassembly 102 and/or system 100 is used in conjunction with the sensedinformation. Alternatively or additionally, the separation distances 110measured by the assembly 102 can be collected along with a time stamp orother marker such as geographic location without communicating directlywith the other sensors, controller, computer, and the like. Thesoftware-implemented system can then reconcile the separation distance110 and other sensor data to align the measurements with each other.

The examples of sensor fusion described herein are not limited to justthe combination of the sensing assembly 102 and one other sensor.Additional sensors may be used to aggregate the separation distances 110and/or motion detected by the sensing assembly 102 with the data streamsacquired by two or more additional sensors. For example, audio data(from a microphone), video data (from a camera), and the separationdistances 110 and/or motion from the sensing assembly 102 can beaggregated to give a more complete understanding of a physicalenvironment.

FIG. 28 is a schematic diagram of a sensing system 2800 that may includethe sensing assembly 102 in accordance with one embodiment. The sensingsystem 2800 includes a sensor 2802 that obtains lateral size data of atarget object 2804. For example, the sensor 2802 may be a camera thatobtains a two dimensional image of a box or package. FIG. 29 is aschematic diagram representative of the lateral size data of the targetobject 2804 that is obtained by the sensor 2802. The sensor 2802 (or acontrol unit communicatively coupled with the sensor 2802) may measuretwo dimensional sizes of the target object 2804, such as a lengthdimension 2806 and a width dimension 2808. For example, atwo-dimensional surface area 2900 of the target object 2804 may becalculated from the image acquired by the sensor 2802. In oneembodiment, the number of pixels or other units of the image formed bythe sensor 2802 can be counted or measured to determine the surface area2900 of the target object 2804.

FIG. 30 is another view of the sensing assembly 102 and the targetobject 2804 shown in FIGS. 28 and 29. In order to calculate the volumeor three dimensional outer surface area of the target object 2804, thesensing assembly 102 may be used to measure a depth dimension 2810 ofthe target object 2804. For example, the sensing assembly 102 maymeasure the separation distance 110 between the sensing assembly 102 anda surface 3000 (e.g., an upper surface) of the target object 2804 thatis imaged by the sensor 2802. If a separation distance 3002 between thesensing assembly 102 and a supporting surface 3004 on which the targetobject 2804 is known or previously measured, then the separationdistance 110 may be used to calculate the depth dimension 2810 of thetarget object 2804. For example, the measured separation distance 110may be subtracted from the known or previously measured separationdistance 3002 to calculate the depth dimension 2810. The depth dimension2810 may be combined (e.g., by multiplying) with the lateral size data(e.g., the width dimension 2808 and the length dimension 2806) of thetarget object 2804 to calculate a volume of the target object 2804. Inanother example, the depth dimension 2810 can be combined with thelateral size data to calculate surface areas of each or one or moresurfaces of the target object 2804, which may then be combined tocalculate an outer surface area of the target object 2804. Combining thedepth data obtained from the sensing assembly 102 with the twodimensional, or lateral, data obtained by the sensor 2802 may be usefulin applications where the size, volume, or surface area of the targetobject 2804 is to be measured, such as in package shipping,identification or distinguishing between different sized target objects,and the like.

FIG. 26 is a schematic diagram of another embodiment of a sensing system2600. The sensing system 2600 may be similar to the system 100 shown inFIG. 1. For example, the system 2600 may include a sensing assembly 2602(“Radar Unit”) that is similar to the sensing assembly 102 (shown inFIG. 1). Although the sensing assembly 2602 is labeled “Radar Unit” inFIG. 26, alternatively, the sensing assembly 2602 may use anothertechnique or medium for determining separation distances 110 and/ordetecting motion of a target object 104 (e.g., light), as describedabove in connection with the system 100.

The assembly 2602 includes a transmitting antenna 2604 that may besimilar to the transmitting antenna 204 (shown in FIG. 2) and areceiving antenna 2606 that may be similar to the receiving antenna 206(shown in FIG. 2). In the illustrated embodiment, the antennas 2604,2606 are connected to the assembly 2602 using cables 2608. The cables2608 may be flexible to allow the antennas 2604, 2606 to bere-positioned relative to the target object 104 on-the-fly. For example,the antennas 2604, 2606 may be moved relative to the target object 104and/or each other as the transmitted signals 106 are transmitted towardthe target object 104 and/or the echoes 108 are received off the targetobject 104, or between the transmission of the transmitted signals 106and the receipt of the echoes 108.

The antennas 2604, 2606 may be moved to provide for pseudo-bistaticoperation of the system 2600. For example, the antennas 2604, 2606 canbe moved around to various or arbitrary locations to capture echoes 108that may otherwise be lost if the antennas 2604, 2606 were fixed inposition. In one embodiment, the antennas 2604, 2606 could be positionedon opposite sides of the target object 104 in order to test for thetransmission of the transmitted signals 106 through the target object104. Changes in the transmission of the transmitted signals 106 throughthe target object 104 can indicate physical changes in the target object104 being sensed.

This scheme can be used with greater numbers of antennas 2604 and/or2606. For example, multiple receiving antennas 2606 can be used todetect target objects 104 that may otherwise be difficult to detect.Multiple transmitting antennas 2604 may be used to illuminate targetobjects 104 with transmitted signals 106 that may otherwise not bedetected. Multiple transmitting antennas 2604 and multiple receivingantennas 2606 can be used at the same time. The transmitting antennas2604 and/or receiving antennas 2606 can be used at the same time,transmitting copies of the transmitted signal 106 or receiving multipleechoes 108, or the sensing assembly 2602 can be switched among thetransmitting antennas 2604 and/or among the receiving antennas 2606,with the observations (e.g., separation distances 110 and/or detectedmotion) built up over time.

FIGS. 27A-B illustrate one embodiment of a method 2700 for sensingseparation distances from a target object and/or motion of the targetobject. The method 2700 may be used in conjunction with one or more ofthe systems or sensing assemblies described herein.

At 2702, a determination is made as to whether to use to the coarsestage determination of the time of flight and/or separation distance.For example, an operator of the system 100 (shown in FIG. 1) maymanually provide input to the system 100 and/or the system 100 mayautomatically determine whether to use the coarse stage determinationdescribed above. If the coarse stage determination is to be used, flowof the method 2700 proceeds to 2704. Alternatively, flow of the method2700 may proceed to 2718. In one embodiment, the coarse stage uses asingle channel (e.g., either the I channel or the Q channel) of thetransmitted signal and received echo signal to determine the time offlight and/or separation distance, also as described above.

At 2704, an oscillating signal is mixed with a coarse transmit patternto create a transmitted signal. For example, the oscillating signal 216(shown in FIG. 2) is mixed with a digital pulse sequence of the transmitpattern signal 230 (shown in FIG. 2) to form the transmitted signal 106(shown in FIG. 1), as described above.

At 2706, the transmitted signal is transmitted toward a target object.For example, the transmitting antenna 204 (shown in FIG. 2) may transmitthe transmitted signal 106 (shown in FIG. 1) toward the target object104 (shown in FIG. 1), as described above.

At 2708, echoes of the transmitted signal that are reflected off thetarget object are received. For example, the echoes 108 (shown inFIG. 1) that are reflected off the target object 104 (shown in FIG. 1)are received by the receiving antenna 206 (shown in FIG. 2), asdescribed above.

At 2710, the received echoes are down converted to obtain a basebandsignal. For example, the echoes 108 (shown in FIG. 1) are converted intothe baseband echo signal 226 (shown in FIG. 2). For example, thereceived echo signal 224 may be mixed with the same oscillating signal216 (shown in FIG. 2) that was mixed with the coarse transmit patternsignal 230 (shown in FIG. 2) to generate the transmitted signal 106(shown in FIG. 1). The echo signal 224 can be mixed with the oscillatingsignal 216 to generate the baseband echo signal 226 (shown in FIG. 2) asthe coarse receive data stream, as described above.

At 2712, the baseband signal is digitized to obtain the coarse receivedata stream. For example, it may pass through the baseband processor 232including the digitizer 730 to produce the digitized echo signal 740.

At 2714, a correlation window (e.g., a coarse correlation window) and acoarse mask are compared to the data stream to identify a subset ofinterest. Alternatively, the mask (e.g., a mask to eliminate or changeone or more portions of the data stream) may not be used. In oneembodiment, the coarse correlation window 320 (shown in FIG. 3) thatincludes all or a portion of the coarse transmit pattern included in thetransmitted signal 106 (shown in FIG. 1) is compared to various subsetsor portions of the digitized echo signal 740 (shown in FIG. 2), asdescribed above. Correlation values can be calculated for the varioussubsets of the data stream 226, and the subset of interest may beidentified by comparing the correlation values, such as by identifyingthe subset having a correlation value that is the greatest or is greaterthan one or more other subsets of interest.

At 2716, a time of flight of the transmitted signal and echo iscalculated based on a time delay of the subset of interest. This time offlight can be referred to as a coarse time of flight. As describedabove, the subset of interest can be associated with a time lag (t_(d))between transmission of the transmitted signal 106 (shown in FIG. 1) andthe first bit of the subset of interest (or another bit in the subset ofinterest). The time of flight can be equal to the time lag, or the timeof flight can be based on the time lag, with a correction or correlationfactor (e.g., for the propagation of signals) being used to modify thetime lag to the time of flight, as described above.

At 2718, a determination is made as to whether the fine stagedetermination of the separation distance is to be used. For example, adetermination may be made automatically or manually to use the finestage determination to further refine the measurement of the separationdistance 110 (shown in FIG. 1) and/or to monitor or track motion of thetarget object 104 (shown in FIG. 1), as described above. If the finestage is to be used, then flow of the method 2700 may proceed to 2720.On the other hand, if the fine stage is not to be used, then flow of themethod 2700 may return to 2702.

At 2720, an oscillating signal is mixed with a digital pulse sequence tocreate a transmitted signal. As described above, the transmit patternthat is used in the fine stage may be different from the transmitpattern used in the coarse stage. Alternatively, the transmit patternmay be the same for the coarse stage and the fine stage.

At 2722, the transmitted signal is communicated toward the targetobject, similar to as described above in connection with 2706.

At 2724, echoes of the transmitted signal that are reflected off thetarget object are received, similar to as described above in connectionwith 2708.

At 2726, the received echoes are down converted to obtain a basebandsignal. For example, the echoes 108 (shown in FIG. 1) are converted intothe baseband echo signal 226 (shown in FIG. 2).

At 2728, the baseband signal 226 is compared to a fine receive pattern.The fine receive pattern may be delayed by the coarse time of flight, asdescribed above. For example, instead of comparing the baseband signalwith the receive pattern with both the baseband signal and the receivepattern having the same starting or initial time reference, the receivepattern may be delayed by the same time as the time delay measured bythe coarse stage determination. This delayed receive pattern also may bereferred to as a “coarse delayed fine extraction pattern” 728.

At 2730, a time lag between the fine data stream and the time delayedreceive pattern is calculated. This time lag may represent the temporaloverlap or mismatch between the waveforms in the fine data stream andthe time delayed receive pattern, as described above in connection withFIGS. 8 through 11. The time lag may be measured as the energies of thewaveforms that represent the overlap between the fine data stream andthe time delayed receive pattern. As described above, time periods 808,810, 904, 906 (shown in FIGS. 8 and 9) representative of the time lagmay be calculated.

At 2732, the time of flight measured by the coarse stage (e.g., the“time of flight estimate”) is refined by the time lag. For example, thetime lag calculated at 2730 can be added to the time of flightcalculated at 2716. Alternatively, the time lag may be added to adesignated time of flight, such as a time of flight associated with orcalculated from a designated or known separation distance 110 (shown inFIG. 1).

At 2734, the time of flight (that includes the time lag calculated at2732) is used to calculate the separation distance from the targetobject, as described above. Flow of the method 2700 may then return to2702 in a loop-wise manner. The above methods can be repeated for the Iand Q channels separately or in parallel using parallel paths as in FIG.12 or a switch or multiplexed path as described above to extractdifferences in the I and Q channels. These differences can be examinedto resolve the phase of the echoes.

In one embodiment, performance of the fine stage determination (e.g., asdescribed in connection with 2720 through 2732) is performed on one ofthe I or Q components of channels of the transmit signal and the echosignal, as described above. For example, the I channel of the echosignal 226 (shown in FIG. 2) may be examined in order to measure theamount of temporal overlap between the time-delayed receive pattern andthe echo signal 226, as described above. In order to perform theultrafine stage determination, a similar examination may be performed onanother component or channel of the echo signal, such as the Q channel.For example, the I channel analysis of the echo signal 226 (e.g., thefine stage) may be performed concurrently or simultaneously with the Qchannel analysis of the same echo signal 226 (e.g., the ultrafinestage). Alternatively, the fine stage and ultrafine stage may beperformed sequentially, with one of the I or Q channels being examinedto determine a temporal overlap of the echo signal and the time-delayedreceive pattern before the other of the Q or I channels being examinedto determine a temporal overlap. The temporal overlaps of the I and Qchannels are used to calculate time lags (e.g., I and Q channel timelags), which can be added to the coarse stage determination or estimateof the time of flight. This time of flight can be used to determine theseparation distance 110 (shown in FIG. 1), as described above.Alternatively or additionally, the time lags of the waveforms in the Ichannel and Q channel can be examined to resolve phases of the echoes inorder to calculate separation distance or motion of the target.

As described above, the ultrafine stage determination may alternativelyor additionally involve a similar process as the coarse stagedetermination. For example, the coarse stage determination may examinethe I channel of the receive pattern and the data stream to determinecorrelation values of different subsets of the data stream and, fromthose correlation values, determine a subset of interest and acorresponding time-of-flight, as described herein. The ultrafine stagedetermination can use the Q channel of the receive pattern and the datastream to determine correlation values of different subsets of the datastream and, from those correlation values, determine a subset ofinterest and a time-of-flight, as described above. The times-of-flightfrom the I channel and Q channel can be combined (e.g., averaged) tocalculate a time of flight and/or separation distance to the target. Thecorrelation values calculated by the ultrafine stage determination canbe used to calculate an additional time delay that can be added to thetime delays from the coarse stage and/or the fine stage to determine atime of flight and/or separation distance to the target. Alternativelyor additionally, the correlation values of the waveforms in the Ichannel and Q channel can be examined to resolve phases of the echoes inorder to calculate separation distance or motion of the target.

In another embodiment, another method (e.g., a method for measuring aseparation distance to a target object) is provided. The method includestransmitting an electromagnetic first transmitted signal from atransmitting antenna toward a target object that is separated from thetransmitting antenna by a separation distance. The first transmittedsignal includes a first transmit pattern representative of a firstsequence of digital bits. The method also includes receiving a firstecho of the first transmitted signal that is reflected off the targetobject, converting the first echo into a first digitized echo signal,and comparing a first receive pattern representative of a secondsequence of digital bits to the first digitized echo signal to determinea time of flight of the first transmitted signal and the echo.

In another aspect, the method also includes calculating the separationdistance to the target object based on the time of flight.

In another aspect, the method also includes generating an oscillatingsignal and mixing at least a first portion of the oscillating signalwith the first transmit pattern to form the first transmitted signal.

In another aspect, converting the first echo into the first digitizedecho signal includes mixing at least a second portion of the oscillatingsignal with an echo signal that is based on the first echo received offthe target object.

In another aspect, comparing the first receive pattern includes matchingthe sequence of digital bits of the first receive pattern to subsets ofthe first digitized echo signal to calculate correlation values for thesubsets. The correlation values are representative of degrees of matchbetween the sequence of digital bits in the first receive pattern andthe subsets of the first digitized echo signal.

In another aspect, at least one of the subsets of the digitized echosignal is identified as a subset of interest based on the correlationvalues. The time of flight can be determined based on a time delaybetween transmission of the transmitted signals and occurrence of thesubset of interest.

In another aspect, the method also includes transmitting anelectromagnetic second transmitted signal toward the target object. Thesecond transmitted signal includes a second transmit patternrepresentative of a second sequence of digital bits. The method alsoincludes receiving a second echo of the second transmitted signal thatis reflected off the target object, converting the second echo into asecond baseband echo signal, and comparing a second receive patternrepresentative of a third sequence of digital bits to the secondbaseband echo signal to determine temporal misalignment between one ormore waveforms of the second baseband echo signal and one or morewaveforms of the second receive pattern. The temporal misalignmentrepresentative of a time lag between the second receive pattern and thesecond baseband echo signal is extracted and then the time lag is thencalculated.

In another aspect, the method also includes adding the time lag to thetime of flight.

In another aspect, converting the second echo into the second digitizedecho signal includes forming an in-phase (I) channel of the secondbaseband echo signal and a quadrature (Q) channel of the second basebandecho signal. Comparing the second receive pattern includes comparing anI channel of the second receive pattern to the I channel of the seconddigitized echo signal to determine an I component of the temporalmisalignment and comparing a Q channel of the second receive pattern tothe Q channel of the second digitized echo signal to determine a Qcomponent of the temporal misalignment.

In another aspect, the time lag that is added to the time of flightincludes the I component of the temporal misalignment and the Qcomponent of the temporal misalignment.

In another aspect, the method also includes resolving phases of thefirst echo and the second echo by examining the I component of thetemporal misalignment and the Q component of the temporal misalignment,where the time of flight calculated based on the phases that areresolved.

In another aspect, at least two of the first transmit pattern, the firstreceive pattern, the second transmit pattern, or the second receivepattern differ from each other.

In another aspect, at least two of the first transmit pattern, the firstreceive pattern, the second transmit pattern, or the second receivepattern include a common sequence of digital bits.

In another embodiment, a system (e.g., a sensing system) is providedthat includes a transmitter, a receiver, and a baseband processor. Thetransmitter is configured to generate an electromagnetic firsttransmitted signal that is communicated from a transmitting antennatoward a target object that is a separated from the transmitting antennaby a separation distance. The first transmitted signal includes a firsttransmit pattern representative of a sequence of digital bits. Thereceiver is configured to generate a first digitized echo signal that isbased on an echo of the first transmitted signal that is reflected offthe target object. The correlator device is configured to compare afirst receive pattern representative of a second sequence of digitalbits to the first digitized echo signal to determine a time of flight ofthe first transmitted signal and the echo.

In another aspect, the baseband processor is configured to calculate theseparation distance to the target object based on the time of flight.

In another aspect, the system also includes an oscillating deviceconfigured to generate an oscillating signal. The transmitter isconfigured to mix at least a first portion of the oscillating signalwith the first transmit pattern to form the first transmitted signal.

In another aspect, the receiver is configured to receive at least asecond portion of the oscillating signal and to mix the at least thesecond portion of the oscillating signal with an echo signal that isrepresentative of the echo to create the first baseband echo signal.

In another aspect, the baseband echo signal may be digitized into afirst digitized echo signal and the correlator device is configured tocompare the sequence of digital bits of the first receive pattern tosubsets of the first digitized echo signal to calculate correlationvalues for the subsets. The correlation values are representative ofdegrees of match between the first receive pattern and the digital bitsof the digitized echo signal.

In another aspect, at least one of the subsets of the digitized echosignal is identified by the correlator device as a subset of interestbased on the correlation values. The time of flight is determined basedon a time delay between transmission of the first transmitted signal andoccurrence of the subset of interest in the first digitized echo signal.

In another aspect, the transmitter is configured to transmit anelectromagnetic second transmitted signal toward the target object. Thesecond transmitted signal includes a second transmit patternrepresentative of a second sequence of digital bits. The receiver isconfigured to create a second digitized echo signal based on a secondecho of the second transmitted signal that is reflected off the targetobject. The baseband processor is configured to compare a second receivepattern representative of a third sequence of digital bits to the seconddigitized echo signal to determine temporal misalignment between one ormore waveforms of the second digitized echo signal and one or morewaveforms of the second receive pattern. The temporal misalignment isrepresentative of a time lag between the second receive pattern and thesecond baseband echo signal that is added to the time of flight.

In another aspect, the receiver is configured to form an in-phase (I)channel of the second digitized echo signal and a quadrature (Q) channelof the second digitized echo signal. The system can also include abaseband processing system configured to compare an I channel of thesecond receive pattern to the I channel of the second digitized echosignal to determine an I component of the temporal misalignment. Thebaseband processing system also is configured to compare a Q channel ofthe second receive pattern to the Q channel of the second digitized echosignal to determine a Q component of the temporal misalignment.

In another aspect, the time lag that is added to the time of flightincludes the I component of the temporal misalignment and the Qcomponent of the temporal misalignment.

In another aspect, the baseband processing system is configured toresolve phases of the first echo and the second echo based on the Icomponent of the temporal misalignment and the Q component of thetemporal misalignment. The time of flight is calculated based on thephases that are resolved. For example, the time of flight may beincreased or decreased by a predetermined or designated amount based onan identified or measured difference in the phases that are resolved.

In another embodiment, another method (e.g., for measuring a separationdistance to a target object) is provided. The method includestransmitting a first transmitted signal having waveforms representativeof a first transmit pattern of digital bits and generating a firstdigitized echo signal based on a first received echo of the firsttransmitted signal. The first digitized echo signal includes waveformsrepresentative of a data stream of digital bits. The method alsoincludes comparing a first receive pattern of digital bits to pluraldifferent subsets of the data stream of digital bits in the firstdigitized echo signal to identify a subset of interest that indicatesthe presence and/or temporal location of the first receive pattern thanone or more other subsets. The method further includes identifying atime of flight of the first transmitted signal and the first receivedecho based on a time delay between a start of the data stream in thefirst digitized echo signal and the subset of interest.

In another aspect, the method also includes transmitting a secondtransmitted signal having waveforms representative of a second transmitpattern of digital bits and generating an in-phase (I) component of asecond baseband echo signal and a quadrature (Q) component of the secondbaseband echo signal that is based on a second received echo of thesecond transmitted signal. The second baseband echo signal includeswaveforms representative of a data stream of digital bits. The methodalso includes comparing a time-delayed second receive pattern ofwaveforms that are representative of a sequence of digital bits to thesecond baseband echo signal. The second receive pattern is delayed froma time of transmission of the second transmitted signal by the timedelay of the subset of interest. An in-phase (I) component of the secondreceive pattern is compared to an I component of the second basebandecho signal to identify a first temporal misalignment between the secondreceive pattern and the second baseband echo signal. A quadrature (Q)component of the second receive pattern is compared to a Q component ofthe second baseband echo signal to identify a second temporalmisalignment between the second receive pattern and the second basebandecho signal. The method also includes increasing the time of flight bythe first and second temporal misalignments.

In another aspect, the method also includes identifying motion of thetarget object based on changes in one or more of the first or secondtemporal misalignments.

In another aspect, the first transmit pattern differs from the firstreceive pattern.

It is to be understood that the above description is intended to beillustrative, and not restrictive. For example, the above-describedembodiments (and/or aspects thereof) may be used in combination witheach other. In addition, many modifications may be made to adapt aparticular situation or material to the teachings of the inventivesubject matter without departing from its scope. While the dimensionsand types of materials described herein are intended to define theparameters of the inventive subject matter, they are by no meanslimiting and are exemplary embodiments. Many other embodiments will beapparent to one of ordinary skill in the art upon reviewing the abovedescription. The scope of the subject matter described herein should,therefore, be determined with reference to the appended claims, alongwith the full scope of equivalents to which such claims are entitled. Inthe appended claims, the terms “including” and “in which” are used asthe plain-English equivalents of the respective terms “comprising” and“wherein.” Moreover, in the following claims, the terms “first,”“second,” and “third,” etc. are used merely as labels, and are notintended to impose numerical requirements on their objects. Further, thelimitations of the following claims are not written inmeans-plus-function format and are not intended to be interpreted basedon 35 U.S.C. §112(f), unless and until such claim limitations expresslyuse the phrase “means for” followed by a statement of function void offurther structure.

This written description uses examples to disclose several embodimentsof the inventive subject matter, including the best mode, and also toenable any person of ordinary skill in the art to practice theembodiments disclosed herein, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe subject matter is defined by the claims, and may include otherexamples that occur to one of ordinary skill in the art. Such otherexamples are intended to be within the scope of the claims if they havestructural elements that do not differ from the literal language of theclaims, or if they include equivalent structural elements withinsubstantial differences from the literal languages of the claims.

The foregoing description of certain embodiments of the disclosedsubject matter will be better understood when read in conjunction withthe appended drawings. To the extent that the figures illustratediagrams of the functional blocks of various embodiments, the functionalblocks are not necessarily indicative of the division between hardwarecircuitry. Thus, for example, one or more of the functional blocks (forexample, processors or memories) may be implemented in a single piece ofhardware (for example, a general purpose signal processor,microcontroller, random access memory, hard disk, and the like).Similarly, the programs may be stand alone programs, may be incorporatedas subroutines in an operating system, may be functions in an installedsoftware package, and the like. The various embodiments are not limitedto the arrangements and instrumentality shown in the drawings.

As used herein, an element or step recited in the singular and proceededwith the word “a” or “an” should be understood as not excluding pluralof said elements or steps, unless such exclusion is explicitly stated.Furthermore, references to “one embodiment” of the present inventivesubject matter are not intended to be interpreted as excluding theexistence of additional embodiments that also incorporate the recitedfeatures. Moreover, unless explicitly stated to the contrary,embodiments “comprising,” “including,” or “having” an element or aplurality of elements having a particular property may includeadditional such elements not having that property.

Since certain changes may be made in the above-described systems andmethods, without departing from the spirit and scope of the subjectmatter herein involved, it is intended that all of the subject matter ofthe above description or shown in the accompanying drawings shall beinterpreted merely as examples illustrating the inventive conceptsherein and shall not be construed as limiting the disclosed subjectmatter.

What is claimed is:
 1. A method comprising: transmitting a firstelectromagnetic signal having a first transmit digital bit sequencetoward a target object; receiving an echo of the first electromagneticsignal off the target object; digitizing the echo that is received intoa digitized echo signal; determining a time of flight of the firstelectromagnetic signal and the echo of the first electromagnetic signalby comparing the first transmit digital bit sequence of the firstelectromagnetic signal with a receive digital bit sequencerepresentative of the digitized echo signal; transmitting a secondelectromagnetic signal having a second transmit digital bit sequencetoward the target object; receiving an echo of the secondelectromagnetic signal off the target object; converting the echo of thesecond electromagnetic signal into a baseband echo signal; determining atemporal misalignment between one or more waveforms representative ofthe baseband echo signal and one or more waveforms representative of thesecond electromagnetic signal that are time delayed from transmission ofthe second electromagnetic signal by the time of flight that isdetermined; determining a distance to the target object based on acombination of the temporal misalignment and the time of flight; and oneor more of: recognizing a posture of the target object based on thedistance that is determined; sensing motion of an internal structure ofthe target object based on the distance that is determined; detecting abreathing rate of the target object based on the distance that isdetermined; detecting a heart rate of the target object based on thedistance that is determined; or determining an abdomen size of thetarget object and determining a tidal volume of a breath of the targetobject based on the abdomen size and the distance that is determined. 2.The method of claim 1, wherein the method includes recognizing theposture of the target object based on the distance that is determined.3. The method of claim 1, wherein the method includes sensing the motionof the internal structure of the target object based on the distancethat is determined.
 4. The method of claim 1, wherein the methodincludes detecting the breathing rate of the target object based on thedistance that is determined.
 5. The method of claim 1, wherein themethod includes detecting the heart rate of the target object based onthe distance that is determined.
 6. The method of claim 1, wherein themethod includes determining the abdomen size of the target object anddetermining the tidal volume of the breath of the target object based onthe abdomen size and the distance that is determined.
 7. The method ofclaim 1, further comprising: transmitting a third electromagnetic signaltoward the target object; receiving an echo of the third electromagneticsignal off the target object; determining an in-phase component and aquadrature component of an echo signal that is representative of theecho of the third electromagnetic signal; determining an in-phasecorrelation value representative of a comparison of the in-phasecomponent of the echo signal with one or more of the receive sequence ofdigital bits or a third sequence of digital bits; determining aquadrature correlation value representative of a comparison of thequadrature component of the echo signal with one or more of the receivesequence of digital bits or the third sequence of digital bits; andmodifying the distance that is determined based on one or more of thein-phase correlation value or the quadrature correlation value.
 8. Asystem comprising: one or more antennas configured to transmit a firstelectromagnetic signal having a first transmit digital bit sequencetoward a target object and receive an echo of the first electromagneticsignal off the target object; and one or more processors configured todigitize the echo that is received into a digitized echo signal, the oneor more processors also configured to determine a time of flight of thefirst electromagnetic signal and the echo of the first electromagneticsignal by comparing the first transmit digital bit sequence of the firstelectromagnetic signal with a receive digital bit sequence of thedigitized echo signal, wherein the one or more antennas also areconfigured to transmit a second electromagnetic signal having a secondtransmit digital bit sequence toward the target object and receive anecho of the second electromagnetic signal off the target object, andwherein the one or more processors also are configured to convert theecho of the second electromagnetic signal into a baseband echo signal,the one or more processors configured to determine a temporalmisalignment between one or more waveforms representative of thebaseband echo signal and one or more waveforms representative of thesecond electromagnetic signal that are time delayed from transmission ofthe second electromagnetic signal by the time of flight, the one or moreprocessors also configured to determine a distance to the target objectbased on a combination of the temporal misalignment and the time offlight, wherein the one or more processors also are configured to one ormore of: recognize a posture of the target object based on the distancethat is determined; sense motion of an internal structure of the targetobject based on the distance that is determined; detect a breathing rateof the target object based on the distance that is determined; detect aheart rate of the target object based on the distance that isdetermined; or determine an abdomen size of the target object anddetermining a tidal volume of a breath of the target object based on theabdomen size and the distance that is determined.
 9. The system of claim8, wherein the one or more processors are configured to determine theposture of the target object based on the distance that is determined.10. The system of claim 8, wherein the one or more processors areconfigured to sense motion of the internal structure of the targetobject based on the distance that is determined.
 11. The system of claim8, wherein the one or more processors are configured to detect thebreathing rate of the target object based on the distance that isdetermined.
 12. The system of claim 8, wherein the one or moreprocessors are configured to detect the heart rate of the target objectbased on the distance that is determined.
 13. The system of claim 8,wherein the one or more processors are configured to determine the tidalvolume of the breath of the target object based on the abdomen size andthe distance that is determined.
 14. The system of claim 8, wherein theone or more antennas are configured to transmit a third electromagneticsignal toward the target object and receive an echo of the thirdelectromagnetic signal off the target object, and wherein the one ormore processors are configured to determine an in-phase component and aquadrature component of an echo signal that is representative of theecho of the third electromagnetic signal, determine an in-phasecorrelation value representative of a comparison of the in-phasecomponent of the echo signal with one or more of the receive sequence ofdigital bits or a third sequence of digital bits, determine a quadraturecorrelation value representative of a comparison of the quadraturecomponent of the echo signal with one or more of the receive sequence ofdigital bits or the third sequence of digital bits, and modify thedistance that is determined based on one or more of the in-phasecorrelation value or the quadrature correlation value.
 15. The system ofclaim 8, wherein the one or more processors are configured to determinethe temporal misalignment based on a magnitude of one or moredifferences between the waveforms of the baseband echo signal and thewaveforms of the echo of the second electromagnetic wave.
 16. The systemof claim 15, wherein the one or more processors are configured tocompare the magnitude of the one or more differences between thewaveforms of the baseband echo signal and the waveforms of the echo ofthe second electromagnetic wave to thresholds associated with differentdesignated times, the one or more processors also configured todetermine the temporal misalignment based on which of the thresholdsthat the magnitude exceeds.